Heating boiler pressure reducing or water feeder valve questions and answers.

This article series explains hot water boiler (hydronic heat) pressure reducing valves and types of manual and automatic water feeder valves used on hot water heating boilers, including when and how to add makeup water to a boiler.

Hydronic (hot water) Heating Boiler Pressure Reducer / Water Feed Valve FAQs

The illustrations here show a modern automatic pressure-reducing water feeder valve on a hydronic (hot water) heating boiler - one of the safety controls which we discuss in this article. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

On many heating boilers the expansion tank and water feeder valve are separate physical units.

On these older systems the "automatic water feeder" is often a bell-shaped device which opens and sends makeup water into the heating boiler and its piping whenever the heating system's internal water pressure falls below a normal level (perhaps 12 psi when the boiler is cold).

How do you test the water pressure from the automatic water feeder

On a hot water boiler how do you test the water pressure from the automatic water feeder? On 2020-01-20 by Thomas

Answer by (mod) - normal residential hydronic heating boiler pressure level

1. Thomas
   
   When the boiler is cold you will, on a typical residential system see about 12 psi in the boiler. - look at the boiler pressure / temperature gauge.
   
   If you're not sure what that gauge looks like or where to find it,
   
   see GAUGES, HYDRONIC BOILER 
   
   
2. If you drain the boiler the water feeder will ror should) re-feed up to that setting, and you'll probalbly hear water running into the boiler.
3. Read the boiler pressure on the on the boiler temperature/pressure gauge (not that those are lab-precise)
4. When the boiler is completely cold, for a residential building of two stories in height above ground, you should see a water pressure of about 12 psi.
5. When the boiler is fully hot, has been running for some time in response to a call for heat, you should see water pressure well above 12 psi, but under 30 psi.

The boiler gauge above shows normal a operating temperature and pressure when the boiler has been running and is therefore hot.

Why is my boiler pressure gauge showing zero?

As a retired pipe fitter I installed a Peerless MIH11-05 in Sept.2019 .

Water feeder was set for 18lbs EX-30 was set for 18lbs.

When boiler cycles it goes to 23lbs but when it shuts down and cools off the press.gage shows zero lbs why is this .

When boiler cycles again it goes up 23lbs.

Everything is new with a Spirovent Air Eliminator and boiler has heating good

I’m just baffled by the zero gage reading in the off cycle On 2020-01-10 by Phil

by (mod) - explanation of boiler pressures & warning about clogged gauge that stops showing pressure

Phil

In a typical residential hot water boiler the pressure of the boiler when cold is set to about 12 psi. When the boiler gets hot, up to just under 200F, the relief valve will stay shut.

If our starting pressure exceeds 30 psi the TPR valve would dump;

If your pressure never gets above 23 psi then - when you check the TPR valve you ought to see no spillage there.

So could we have a leak or a bad gauge?

If you tap on the gauge does the needle jump up?

Is the gauge a combination temp and pressure unit? If so does it show temperature? What temp are you seeing?

Watch out: often rust or sediment clog a boiler pressure gauge so that it stops reading at all or gives inaccurate readings.

See details at GAUGES, HYDRONIC BOILER 

For other readers, the Peerless MIHII-05 is a residential, cast iron, gas-fired hot water heating boiler.

If Phil's boiler were a steam system, it'd show about 0.5 psi hot and close to or at zero psi when the steam boiler is off and cold.

by Phil

I meant to say the is heating good. Water feeder valve was turned off after Initial fill up

Reply by (mod) -

Phil

Usually there is a pressure reducer/water feeder that's left with live feed into it, thence feeding into the boiler (manufacturers warn against this common practice).

In any event if you turn off water in to a hydronic heating boiler (that's hot water, not steam) you ought not see the boiler system losing water (and pressure). If you see the COLD pressure fall below the initial pressure then there's most-likely a leak to find and fix.

For a 4th floor apartment what should the boiler pressure be?

There is a 45l psi pressure regulator on a boiler that heats an apt on the 4 th floor what should the expansion tank psi be set at? On 2019-12-26 by eddie

by (mod) - 45L or 451 psi? This sounds like an error. Boiler pressure is set by the water feeder not the expansion tank.

Eddie

Apologies but I'm not at all familiar with a heating system that would operate at over 400 PSI according to your note. I hope that you simply made a typographical error.

For a building whose boiler has to lift or push hot water up four floors from the level of the boiler itself I'd expect the boiler and water system psi to range between 18psi cold to about 25-26 psi hot.

We do not set boiler pressure by controls on the expansion tank.

The boiler pressure is set by the boiler's water feeder mechanism.

Watch out: Very high pressure and hot water heating system risks a fatal catastrophic boiler explosion.

You need to have your system inspected and serviced by a qualified, trained heating person to be sure that it is safe.

Reference: 2024 International Mechanical Code, Chapter 10, Boilers, Water Heaters and Pressure Vehicles (ICCSafe Website)

See Section IMC 1005, Boilers, through Section 1006, Safety and Pressure Relief Valves and Controls

Does pressure reducing valve require a "slow water feed rate" from the water source?

Does the water from the well pump or city need to be feed at a slow rate to the reducing valve, to make the reducing valve work correctly and control the pressure in the boiler ?

I asking about a fill after replacing the pressure reducing valve.

It has been replaced twice and does not stop at the proper boiler pressure and continues to overfill. I was told that the valve that provides the outside water just needs to be barley open to fill the boiler so the reducer can overcome the fill pressure be allowed to close and work correctly? On 2019-12-17 by holly blumenberg

by (mod) - It's not feed rate but it is feed pressure, as we detail here

Holly

I think the question you want to ask is not "rate" of water since that would be measured in volume over time or GPM for example, but rather pressure.

The reducing valve will be rated for a maximum inlet pressure. On typical residential systems that's probably under 80 psi.

Opening or closing a valve part-way changes the flow rate but not the inlet pressure.

Should the automatic water feeder valve handle be normally "up" or "down"?

does the handle on the bell stay up or down? i get this confused On 2019-12-03 by jan

Answer by (mod) - Down for normal operation, Up for bypass

Up would be in temporary bypass mode. Handle down is normal.

How do I monitor the water level in my hydronic boiler that doesn't use a sight glass

Thanks again for all your efforts to educate the 'Great Unwashed' as my mother would say.

We were discussing my hydronic boiler system in a commercial building that we purchased to convert to a home (former police station).

The hydronic boiler has a small leak (loss of pressure of 1# per week typical) and I leave the cold water make up water valve shut off because the pressure regulator allows the pressure to go too high.

I have limited options during this heating season (it has already been -25C here!) so changing valves and adding leak-stop will have to wait until Summer.

Note: there's a 1 1/2" gate valve on the return side of zone 2 (2 zone system) that has been leaking for quite awhile, I would guess via the packing gland. This morning I attacked it with a (brass) wire brush and cleaned the white salts and green corrosion off as best I could. I then closed the valve a bit - and water issued forth (quite a bit of flow).

Re-opened the valve fully and grabbed my thumb-wrench. Closed the valve again a bit and tried tightening the gland nut - wouldn't move at first but I gradually increased my torque and eventually...tighter and the leaking stopped.

Re-opened the valve fully and did some more cleaning (more debris loosened due to the moisture). Opened the make-up water valve and bumped the pressure back to 15# so I can monitor whether I've improved my leaking problem.

My question: you say (quite emphatically) that the pressure regulator valve is not to be relied upon to keep the system safe (manufacturers state the same credo). You suggest using a float-controlled fill valve in conjunction with the rest of the system (to prevent the water level from dropping below the safe level and risking death and destruction).

I did some research after our last correspondence, found some Mcdonnell & Miller float-operated fill valves and studied them carefully.

However, my system does not have a sight glass and I have no idea where the 'normal' operating water level should be.

Is there another way to determine the water level and therefore where to position the float-controlled valve? - On 2019-11-27 by Starm

by (mod) - How to monitor water level in a leaky hydronic boiler

So we're talking about a hot water heating boiler - not a steam boiler, right? If so there would not be a sight glass;

IF your boiler doesn't already have one, you can

• Watch the boiler pressure and temperature gauge to be sure it stays in normal operating range, including at a bottom of 12 psi when the boiler is cold
  
  See GAUGES, HYDRONIC BOILER to understand how to read the pressure/temperature gauge on your boiler.
• Add a LWCO for hot water boilers, or you would watching for a steaming venting TPR valve or maybe hearing bubbling gurgling boiling at the boiler.
• Watch out: if you see water discharging or steaming at the pressure/temperature relief valve your boiler is unsafe and needs to be shut down and repaired
  

Bottom line:

With the boiler COLD you'd add water until the boiler water pressure is at 12 psi at the pressure gauge (That's the normal COLD pressure in the boiler for a typical one family two story home)

Be very careful about wire brushing picking chopping hacking or fooling with old plumbing parts. Sometimes you convert a small drip or leak into a horrible gusher.

Followup by Star: I cleaned the valve in my first photo but still don't get how to monitor boiler water level

Great reply, thanks!
I know I was taking a chance with my cleaning on that old valve - but I didn't want to try and tighten the gland nut without removing the abrasive buildup first, and I was successful in the end (thank the lord and pass the biscuits).

About my question: no sight glass on my system, the only system monitors I have are: two analog thermometers just above the two circulation pumps and the system pressure gauge.

So how do I monitor my water level? Tap the pipe with a hammer?

by (mod) - your boiler has an automatic water feeder; just watch the pressure gauge. Watch out for some safety questions we raise below.

While a few hot water (hydronic - not steam) boilers include a low water cutoff control, they're not common on residential hot water boilers.

But I can see why you're confused about the controls on your boiler. It's possible that earlier in its life the boiler in your photo was providing steam heat to this home, later converted to hot water (hydronic) Heat. The boiler may have previously burned coal or oil. (See my warning below about the flue damper).

I have labelled some of the boiler parts in your photo and you'll see at the upper left over the boiler there is a McDonnel Miller Water Feeder Valve.

Photo above: a Warden King cast iron boiler with a Flame-Master gas burner. The boiler appears to be covered with asbestos.

Warden King boilers were sold configured to use in both hot water heating and steam heating systems.

We detail those valves as they were used for steam heating boilers are

at WATER FEEDER VALVE, STEAM. It's not hurting you a bit to have it on the system - your service tech can clean the strainer and be sure this control is working.

You don't need and won't normally find a sight glass on a hydronic (hot water) heating boiler. Your boiler and pipes are kept always full of water - by a water feeder valve.

Watch out: in your photo I've labelled a barometric damper as "FLUE DAMPER" and we see in the photo that it's quite widely open - a condition that significantly cuts the draft seen by the gas burner in this boiler.

Be sure your service technician checks that the burner is operating properly and that the draft is proper. Inadequate draft on a gas burner risks fatal carbon monoxide poisoning.

(Be sure you have working CO and smoke detectors throughout the home.)

Watch out: from your photo it looks to me as if your boiler may be covered with asbestos insulation. Avoid damaging or disturbing the insulating cover.

To be clear, an automatic water feeder valve for a hot water (not steam) heating boiler generally operates simply by monitoring pressure in the system, keeping the boiler pressure at around 12 psi when the systm is cold.

See PRESSURE REDUCER / WATER FEED VALVE, BOILER to understand those devices.

See FLAME-MASTER FURNACES, Bow Valley Resources Gas Furnaces, Calgary - to find a manual for your heater.

See WARDEN KING BOILERS - to find out more about your Warden heating boiler, age, history, manuals.

by Star: how can I install a water feeder if there is no low water cutoff or water level indicator on my boiler

Thank you!

Yes - hot water heating boiler is what I have.

So if I don't know where the 'normal' water level is, how can I install a float-operated water fill valve which iswhat you recommended to me in my previous correspondence?

I understand that the FOFV has to be installed in line with the 'normal' water level in order to maintainthat level for safe operation of the boiler.

The one I was looking at also had a LWCO built in.

Moderator reply: Yours is a hot water (not steam) hydronic heating boiler and all of the piping should normally always be full of water

Watch out: hot water boilers are normally always completely full of water as is the piping. Otherwise the risks include

No heat to some or all of the building

and in the worst case damage or complete desctruction of the boiler if it's heated without enough or any water inside.

That's why you'd want an automatic water feed valve installed and you want any boiler leaks repaired promptly

That Flame-Master gas burner may well have been a modification to what was originally a coal burning heating boiler. How old is your home?

What's the cost of a water feed valve for my heater?

How much is a water feeder valve on my furnace - On 2019-05-15 by Bill

Answer by (mod) -

Bill

A simple pressure-reducing valve may be about $60. U.S.

An automatic water feeder on a steam boiler is around $200.

How to fix too much variation in boiler water pressure

I just replaced the back flow prevented , the water pressure regulator , and the expansion tank for boiler.

The water pressure in the boiler fluctuates all over the place from 20 psi up to 40 psi.

I cannot get the pressure in the boiler to stay somewhat constant. My pressure relief valve keeps dripping when the pressure exceeds 30 psi. How should this be corrected. - On 2018-10-23 by Bob

Explanation by (mod) - how to diagnose improper or continuous water feeding into the boiler

That sounds to me like a damaged water feeder valve or a tankless coil leak INTO the boiler.

There are two common explanations:

A leaky pressure reducing valve can continue to send water into a boiler when it shouldn't

- see PRESSURE REDUCING VALVE TROUBLESHOOTING, INSPECTION, SERVICE & REPAIR PROCEDURE

A leaky tankless coil leaking into the boiler. Is there a tankless coil on your heater?

- see TANKLESS COIL INTERNAL LEAKS INTO the BOILER

How do I fix strange variations in boiler pressure and house water pressure

I could use some assistance, so here goes:

The furnace and radiators were recently replaced in my home. Whole new setup.

The suspicious behaviors:

1. We noticed that after the furnace had run, using the cold water at any tap in the house resulted in a strong, temporary (few seconds) burst of high pressure cold water.

We told the plumber; after telling us he'd never seen such a thing, he came back and installed two pressure relief tanks, one on each water heater. That got rid of the pressure issue.

2. Now, often when the cold water is turned on (again, any tap), the furnace turns on if it has not been on for a bit. It's not every time, but it's far too often to be coincidence. I can get up at 3am, walk into the kitchen, turn on the cold water, and in less than one second the furnace turns on.

Coincidence? How about several times every day?

3. The igniter on the unit already needed replacing after one year.

New guys came out and while they were here, they noted that the pressure was high in the unit (33lbs/in2). They drained the pressure down to 14 and closed the valve off again.

They told me, "This is a fully closed system, so this shouldn't happen.

The house could be dry and this would keep circulating the same water." After the igniter was changed, approx 2 weeks later, the furnace stopped working again. Instead of blowing my brains out (you have no idea the number of problems we've had with heating in this house

-- the unit was even replaced for a house fire when the last unit burned up) I went down and tried to figure out the problem myself. Turns out, the pressure in the unit was 2.3lbs/in2. Yes, 2.3. The unit wouldn't fire because it was a vacuum inside.

So I opened the valve the last plumber closed, let it equalize to where it should be, and reset the unit. It started running fine again and has since.

So to understand: with the valve open, the pressure goes between 14 and 30 when in use. With it closed, it drops to 2 within a couple of weeks.

That is NOT a closed system.

My suspicion, based on the behaviors described above, is that the first plumber either hooked us up wrong or the valve is shot, but whatever the cause, the system is NOT closed. So ... are we drinking radiator/furnace water?

Thanks for any insights. On 2018-02-03 by DW

by (mod) - If boiler pressure drops abnormally low when the boiler isn't in use

DW

If the pressure drops to less than 12 psi in the heating boiler during a period of non-use and never falls below that I suspect that you're simply seeing a pressure gauge that was slightly stuck.

I would infer that if there were a leak, pressure will continue to fall.

But there might be some conditions under which A fitting only leaks when the the system is hot, or under pressure.

See PRESSURE REDUCING VALVE (BOILER) CLOG REPAIR

Separately, it is indeed bizarre for the operation of a heating boiler (furnaces are hot air heat, you have a heating boiler not a furnace) to have any effect on cold water pressure in the home.

However if you have steam heat (that always consumes some water in the steam boiler and piping) it is normal for the boiler to take on some additional water through an automatic water feeder at frequent intervals, possibly even at every boiler-on cycle.

IF also your home water pressure regulator is sticking then building water pressure may fall, then when water is run the pressure regulator may "un-stick" and increase building water pressure. ]

Other building water pressure regulator anomalies can also produce irregular water pressure behaviour in the building.

See WATER PRESSURE REGULATOR ADJUSTMENT

Can a heating boiler be "over-filled"?

can a boiler be over filled? On 2016-12-30 by Anonymous John

Answer by (mod) - no but it can be over-pressureized

Anon: John:

Not exactly over-filled, but over-pressurized.

The boiler and hot water piping, radiators, etc. are normally filled to eliminate all air and (in a typical residential building) set to 12 psi cold.

If you over-pressurize the boiler your relief valve will spill when the system heats up - repreated TPR valve spilling is unsafe.

Please see HOT WATER PRESSURE EXPANSION RATE found at https://inspectapedia.com/plumbing/Hot_Water_Expansion.php

A hydronic - hot water heating - boiler can't be over-filled by volume as the system is (with exception of the expansion tank) always full of water.
But you will want to read

HEATING BOILER WATER PRESSURE (see ARTICLE INDEX)

Watch out: A steam boiler can be over-filled.

What causes noise at the water pressure reducing / feeder valve?

Why is the reducing valve making noise when feeds water into the boiler? On 2016-11-25 by Nazario leon

Answer by (mod) - dirt on a valve seat or a damaged diaphragm in the reducing valve.

Nazario

I can but guess that there is dirt on a valve seat or a damaged diaphragm in the reducing valve.

How often should the automatic water fill valve add water to a boiler?

We just installed a new boiler with an automatic water fill valve. How often is the valve supposed to kick in and add water? On 2016-06-03 by Clem Boer

Explanation by (mod) - it depends: for a hot water system, almost never, for steam boilers, daily

Clem if yours is a hydronic (hot water) heating system, rarely will the water feeder have anything to do; only at service or if the boiler is drained; the valve will however protect the boiler from damage due to loss of water by keeping water in it should a leak occur. (For extra safety you can add a low water cutoff valve to some boilers)

If it's a steam boiler, frequently, perhaps daily or even more often depending on how much the boiler is running, the feeder will have to add water.

 

Can't I just use a manual valve to feed water to my boiler?

Why not just use a manual ball valve for water feed ? On 2015-10-31 by Joe

by (mod) - A manual valve is a good addition to the automatic valve and is usually upstream of the automatic water feeder.

Joe:

A manual valve is a good addition to the automatic valve and is usually upstream of the automatic water feeder.

But if you use a manual-only water feeder, unless your boiler also includes a low water cutoff safety valve, if there's ever a leak the risk is a ruined boiler or even worse, a fire or explosion if there is a combination of failures.

And there's the inconvenience of having to regularly monitor the system to add water.

Can a leaky pressure reducing valve back-feed boiler water into the domestic water piping system?

Water Pressure-Reducing Feed Valve is hot back along the supply line. If the valve is leaking can sediment get into domestic water system? On 2015-04-30 by Norman

by (mod) - yes

Norman

Yes, not just sediment but any contaminants in the heating system water can enter the building water supply.

But before assuming that there is a leak, consider whether heat from the heating system is simply being conducted through the metal piping itself. If heating water is backfeeding into the house supply I'd expect that dirty water to show up at the output of the nearest faucet.

Why do I have to keep adding water to my boiler?

(Jan 16, 2012) Bob

why do i have to add water daily to my boiler

Reply:

Bob:
If you are having to add water to your boiler too often either there is a leak somewhere (a condensate line, or hidden in the boiler itself), or steam vents are not closing when they should. Or an automatic water feeder on your system is not working.

 

Expansion tank (or relief valve) keeps discharging water as service water pressure varies

I have a gravity feed system with water radiators in my home.

When I leave the incoming water on the pressure in my system goes sky high the expansion tank discharges the water. When my system is full of water and I turn off the incoming water by the water feeder my system loses pressure and I have to add water again thru the water feeder. Is my water feeder the issue?

When the system loses pressure where is that water going?? The expansion tank is above my furnace in my basement. Any help would be appreciated!! Thanks, Fred

In regards to my gravity feed system "pressure" problem question -- Municipal water, system has been working fine for last 15 yrs. When system full of water home heats fine but when furnace off pressure drops. Thanks, Fred

Reply:

Fred,

Particularly with a gravity circulating system, that is you rely on hot water rising through the heating pipes by convection rather than by using a circulator pump, if there is not enough pressure in the heating system hot water may rise too slowly or even not at all to upper floors in the building.

Check the water pressure in your heating boiler (furnaces are hot air systems, water based heating systems are boilers) when the system is cold - for a typical 2 story home you'll want to see 12 psi cold pressure in the boiler.

If your boiler pressure is low and/or if you've had a leak and lost boiler water leading to low pressure AND if your water feeder valve is not working properly (or is not properly set) then you may have low boiler pressure.

Also take a look at "What is the proper water pressure setting for a pressure-reducing valve or water feeder valve on a Hot Water Heating System?" in the article PRESSURE REDUCER / WATER FEED VALVE, BOILER

 

My house is too hot and the boiler circulator keeps going even if I turn down the thermostat

The circulator pump on my Weil Mclain boiler doesn't respond to the thermostat. I closed the manual flow valve to prevent the baseboards from "heating" during the summer.

I recently had to open the valve to provide heat to the house now that it has gotten colder but when the house heated up too hot the flow valve would not close and the baseboards continued to receive hot water.

How can I "fix" the valve to shut off the water supply to the baseboards?

Will i need to purge the water from the zone to replace the valve? - House too hot 12/21/11

Reply:

House too hot:

You're asking a question under an article on automatic water feeders -- valves that maker sure the water in a heating boiler is kept at proper level. This won't help you with a heat control issue.

Under BOILERS HEATING (links at the ARTICLE INDEX the bottom of this article ) you'll

see BOILER CONTROLS & SWITCHES - an article that lists various boiler controls. Your control problem could be in any of several places

• the wall room thermostat -
  
  THERMOSTATS, HEATING / COOLING
• the circulator control and relay switch (good guess) -
  
  see CIRCULATOR PUMPS & RELAYS
• and the flow control valve - which should act as a check valve to prevent hot water from circulating up out of the boiler when you are not calling for heat -
  
  see CHECK VALVES, HEATING SYSTEM.

Fixing the problem by opening and closing the flow-control valve is a stopgap that as you have seen, is not a great solution.

Your system may have two faults:

1. the hot water should not be circulating out of the boiler in summer when you never call for heat - this is a flo control check valve problem, presuming that there is some reason that the boiler is hot in the first place (like keeping it hot for making domestic hot water)

2. the circulator may not be responding to the thermostat - sounds like a circulator relay control problem, presuming that it used to work and that no one changed the wiring.

To replace a flow control valve or some circulator pump assemblies that are plumbed directly in line in the hot water heating system, unless there are isolating shutoff valves before and after the device, you'll need to cool down the system, drain the affected piping, replace the part, and indeed, purge air from the lines to restore heat.

Keep us posted - what you learn will help other readers.

 

Top floor radiator is not getting water - should I up the system pressure?

I have a home with 3 levels above the basement, and radiators on every floor.

The radiator at the very top floor does not seem to even contain water, and bleeding does not help. The radiators on the 2nd floor, just below the attic used to heat up fine, but now they do not seem to have water either.

Obviously, there is a pressure issue here, but I had the water feeder valve for my hydronic system replaced just 4 years ago.

The radiators in the basement and on the first floor work just fine. Can I turn the pressure screw on the water feeder to increase the pressure while the system has been operating for the past 2 months and the boiler is not cool? - Joey Butters 12/31/11

Reply:

Joey I would NOT start by changing system pressure since there is a good chance that your top floor radiator is simply air bound.

Hop over to our radiator troubleshooting articles at RADIATORS for ROOM HEAT and you'll see how to check for and fix an air-bound heating radiator by simply opening an air bleeder.

 

The relief valve at my boiler keeps leaking, even after we replaced it

My boiler has been leaking at the pressure relief valve for 1 week, with the pressure at 30-35 when hot. I drained the steel expansion tank fully, and then re-started the system.

The pressure initially was back down around 20, but within 1 day was back up in the 30s and leaking at the PRV. I had a technician come and install a new pressure reducing valve. We all thought that would fix everything.

We drained the expansion tank again before re-starting the system.

After we re-started the system, the pressure continued to rise. one day later we're back at 33 PSI and draining from the PRV. I tried draining more water from the expansion tank and closing of the water valve from the city. The pressure in the system went down to 20.

After running the heat, it's now hot and at 25 psi. Could I have just gotten a defective new pressure-reducing valve? Any thoughts? Help would be appreciated. - Josh 2/7/12

Reply: flooded expansion tank, over pressure, or over temperature: safety questions

Great question Josh. There are actually several things that can cause the relief valve on a boiler to leak, among them is an automatic water feeder/pressure reducer that is not working properly, but there are quite a few other causes too.

The fact that you drained your expansion tank and then found that you could drain it again makes me suspect that as the best starting place.

If it's an older bladderless type expansion tank (some call these compression tanks) it may be that it wasn't adequately drained. If the expansion tank is a newer type that has an internal bladder the bladder may be damaged or the air valve may be leaking out the air charge.

Details are

at EXPANSION TANKS.

At RELIEF VALVE LEAKS we provide a catalog of all causes of leaks at all types of pressure or pressure / temperature relief valves.

Also see RELIEF VALVE, TP VALVE, BOILER if your boiler is a steam boiler,

or if yours is a hydronic (hot water) system

see RELIEF VALVE, TP VALVE, STEAM BOILER

Watch out: leaky pressure relief valves make your heating system unsafe, risking a boiler explosion or BLEVE explosion.

 

Why the water level in my steam boiler keeps rising?

my sight glass on manual feed boiler rising without adding water I have steam heat system with
an indirect water heater. - Anon 2/23/12

Reply:

Anonymous:

Your water feeder valve may need repair or replacement. Review the diagnostic text in the article PRESSURE REDUCER / WATER FEED VALVE, BOILER

This is particularly likely if the boiler level is actually increasing. Don't confuse increased boiler water level with surging when the steam boiler is heating up.

And don't forget to double check that someone else has not manually added water to the boiler.

Where do I add water to my furnace [sic - boiler]

Need to know where I add water to my furnace. The low water indicator is on. Not sure where to look. And not sure if I have an automatic water feeder. Thank you LJV 109/23/11

Reply:

LJV

Indeed finding where to add water to a steam boiler can be tricky for an unfamiliar building owner because the water supply valves are not always located in the same place.

Try backing up a bit: find the cold water supply piping in your home. Follow the piping to the steam boiler.

That route will show you where water enters the boiler as the piping will end either at a manual valve, at an automatic water feeder valve, or at a combination of the two - that is, some boilers may include an automatic water feed valve as well as a manual valve located on a piping loop that pipes around the water feed valve.

In the links listed at the ARTICLE INDEX the bottom of this article , under STEAM HEATING SYSTEMS
be sure to read the following two articles:

LOW WATER CUTOFF CONTROLS
Water Feeder Valves, Steam

Those articles include photos of the valve(s) you are looking for.

Or use the CONTACT link at the ARTICLE INDEX the bottom of this article to send me some sharp, well-lit photos of your system and I'll be glad to look them over and give more specific advice.

 

Is it ok to turn off the water supply to the heating boiler in winter?

Can a hotwater boiler be operated w/out make up for 2 months during cold weather ? (Sept 30, 2014) Anonymous said:

Going on vacation for 2 months and wondering if it's OK to shut the cold water supply line to the hydronic water heater. This would still allow all the circulation etc but allows me to shut down the main water supply to our house. This system supplies heat to our lower floor only.

I would like to shut the water main off to my house while away. The hydronic heater is separate from the domestic hot water heater.

If OK then the heat would still be available but I would not have the potential problem of water leaks from the plumbing system components such as a cracked toilet tank etc.
Thanks for any comments (Nov 29, 2014) DAN D.

Reply:

It depends, Anon.

If you mean a steam boiler, almost certainly not - the risk is loss of heat or boiler melt-down or worse.

if it's a hydronic (hot water) heating boiler, maybe, if there are are no leaks. But there too if the boiler leaks it could be destroyed or cause very serious damage to the building if the boiler lose heat or explodes from loss of water. If the boiler has a low water cutoff safety valve (as is installed on all steam boilers) then you'd hav some protection from the latter castrophe.

Dan

I sometimes shut off the water main to a home heated by a boiler but *only* if I am very confident that the system is bullet proof and leakproof - the worry is that a leak in the system can destroy the boiler or even lead to a fire.

If the boiler has a low water cutoff valve on it then you're safe: it will simply shut down if it loses water.

Otherwise I would leave water on to the boiler.

In some buildings it's possible to leave the water supply on to the boiler but to shut off all of the hot and cold water supply piping to the rest of the house. That reduces the freeze-burst-pipe damage risk substantially and is worth doing.

Dan see this recent article we put together on this at

WATER TURN OFF? - see inspectapedia.com/plumbing/Winterize_Turn_Water_Off.php

More details about this topic are at our WINTERIZE HEAT ON article

 

What valves do I need on my boiler: why do I have no heat in half of my baseboards?

I have a boiler with two spigots and two silver valves. How do I know which one is the drain and which line the two valves go to?

The copper pipe is in a circle at the boiler and one of the handles is at the top and one is upside down on the bottom (the valve is a circular dial style handle).

I am not receiving heat to half of my base board heat. Do I need to turn one or the other valves? How can I check it? (Nov 18, 2014) Jeqal

Reply:

Jeqal

From just your note, I don't know what valves you are referring to.

Check that each room thermostat for each heating zone is calling for heat - set the thermostat well above room temperatures.

Then check that the boiler is circulating hot water in each heating zones - touch or feel (with care) for hot pipes at each circulator or zone valve.

There could be a thermostat, zone valve, check valve, or even an air bound heating system problem.

It's time to call your heating service technician.

 

How do I know if a water feed valve or TP relief valve is bad?

31 Jan 2015 Anonymous said:
How do I know the feed valve or relirf valve are bad or replace both the relief valve is letting water out. I have a new expansion tank

Reply:

Anon

If you are seeing leaks from the water feeder valve chances are it needs repair or replacement; some water feeders can be repaired using a re-build kit.

But

Watch out: when you also cite that the relief valve is leaking that suggest that either the heating system is at too high a pressure or temperature (unsafe conditions that deserve a system shut-down) or the leaks could be caused by a water-hammer problem at the building or high water pressure or both.

First see RELIEF VALVE LEAKS

then

See WATER HAMMER NOISE DIAGNOSE & CURE

 

What are normal input pressures at a boiler?

(Feb 12, 2015) Anonymous said:
my psi rteads 40 on water inlet gauge. is this too high

Reply:

40 psi is within normal building water supply service pressure ranges.

About water pressure: 40 psi on the street side of the pressure reducer/water feeder valve side of a feed valve for a boiler is ok.

Watch out: But if you are seeing 40 psi on the boiler side, such as on the boiler's gauge, something's wrong and if that's really the pressure you should shut down the system as it is unsafe.

 

What if I can't get water to boiler after flush-out

I shut down boiler and flushed it . When I turned it back on not getting water to boiler - (Feb 24, 2015) Anonymous

Reply:

Anon

Check for a debris-clogged fill valve. Try lifting the valve bypass lever to see if that sends water to the boiler.

The other possibility is that your water shutoff valve is a gate valve that is broken internally.

 

How to fix recurrent air blocked radiators, low psi water feeder

I have a issue with my 4 story building in NYC, top floor, 4floor, (2) apartments have alot of air trapped in the radiator. I installed auto vent valves and still not helping. I force water thru the auto water feeder and that forces the air out of the line and it is fine for a few days. Then air gets trapped again.

I have to force water every 3-5 days during this winter. I believe that my water feeder psi is set at 15 psi. I don't believe it is enough pressure. Based on your input, I may need a different type of auto water feeder, more for commercial.

Every winter we have this issue and not sure what to do next. I tried to get multiple plumbers to look into this matter and they have no idea. Based on your carlson dunlop diagram, I need 20-30 psi pressure for a 4 story building. Please advise it will be greatly appreciated. 16 March 2015 Tony

Reply:

Tony, what you say sounds reasonable to me. If you are seeing recurrent air blockage in all of the radiators of both top floor apartments that strengthens the argument.

What does your heating service company technician say about the water pressure settings?

 

Why do I have to keep adding water to my boiler?

Why do i have to add water daily to my boiler ? (Jan 16, 2012) Bob

Reply:

Bob:
If you are having to add water to your boiler too often either there is a leak somewhere (a condensate line, or hidden in the boiler itself), or steam vents are not closing when they should. Or an automatic water feeder on your system is not working.

 

Expansion tank (or relief valve) keeps discharging water as service water pressure varies

I have a gravity feed system with water radiators in my home. When I leave the incoming water on the pressure in my system goes sky high the expansion tank discharges the water. When my system is full of water and I turn off the incoming water by the water feeder my system loses pressure and I have to add water again thru the water feeder.

Is my water feeder the issue?

When the system loses pressure where is that water going? The expansion tank is above my furnace in my basement. Any help would be appreciated!! Thanks, Fred

In regards to my gravity feed system "pressure" problem question -- Municipal water, system has been working fine for last 15 yrs. When system full of water home heats fine but when furnace off pressure drops. Thanks, Fred

Reply:

Fred,

Particularly with a gravity circulating system, that is you rely on hot water rising through the heating pipes by convection rather than by using a circulator pump, if there is not enough pressure in the heating system hot water may rise too slowly or even not at all to upper floors in the building.

Check the water pressure in your heating boiler (furnaces are hot air systems, water based heating systems are boilers) when the system is cold - for a typical 2 story home you'll want to see 12 psi cold pressure in the boiler.

If your boiler pressure is low and/or if you've had a leak and lost boiler water leading to low pressure AND if your water feeder valve is not working properly (or is not properly set) then you may have low boiler pressure.

Also take a look at "What is the proper water pressure setting for a pressure-reducing valve or water feeder valve on a Hot Water Heating System?" in the article PRESSURE REDUCER / WATER FEED VALVE, BOILER

 

My house is too hot and the boiler circulator keeps going even if I turn down the thermostat

The circulator pump on my Weil Mclain boiler doesn't respond to the thermostat.

I closed the manual flow valve to prevent the baseboards from "heating" during the summer. I recently had to open the valve to provide heat to the house now that it has gotten colder

but when the house heated up too hot the flow valve would not close and the baseboards continued to receive hot water. How can i "fix" the valve to shut off the water supply to the baseboards? Will i need to purge the water from the zone to replace the valve? - House too hot 12/21/11

Reply:

House too hot:

You're asking a question under an article on automatic water feeders -- valves that maker sure the water in a heating boiler is kept at proper level. This won't help you with a heat control issue.

Under BOILERS HEATING (links at the ARTICLE INDEX the bottom of this article ) you'll

see BOILER CONTROLS & SWITCHES - an article that lists various boiler controls. Your control problem could be in any of several places

• the wall room thermostat -
  
  THERMOSTATS, HEATING / COOLING
• the circulator control and relay switch (good guess) -
  
  see CIRCULATOR PUMPS & RELAYS
• and the flow control valve - which should act as a check valve to prevent hot water from circulating up out of the boiler when you are not calling for heat -
  
  see CHECK VALVES, HEATING SYSTEM.

Fixing the problem by opening and closing the flow-control valve is a stopgap that as you have seen, is not a great solution.

Your system may have two faults:

1. the hot water should not be circulating out of the boiler in summer when you never call for heat - this is a flo control valve problem, presuming that there is some reason that the boiler is hot in the first place (like keeping it hot for making domestic hot water)

2. the circulator not responding to the thermostat - sounds like a circulator relay control problem, presuming that it used to work and that no one changed the wiring.

To replace a flow control valve or some circulator pump assemblies that are plumbed directly in line in the hot water heating system, unless there are isolating shutoff valves before and after the device, you'll need to cool down the system, drain the affected piping, replace the part, and indeed, purge air from the lines to restore heat.

Keep us posted - what you learn will help other readers.

 

Top floor radiator is not getting water - should I up the system pressure?

I have a home with 3 levels above the basement, and radiators on every floor. The radiator at the very top floor does not seem to even contain water, and bleeding does not help.

The radiators on the 2nd floor, just below the attic used to heat up fine, but now they do not seem to have water either.

Obviously, there is a pressure issue here, but I had the water feeder valve for my hydronic system replaced just 4 years ago.

The radiators in the basement and on the first floor work just fine. Can I turn the pressure screw on the water feeder to increase the pressure while the system has been operating for the past 2 months and the boiler is not cool? - Joey Butters 12/31/11

Reply:

Joey I would NOT start by changing system pressure since there is a good chance that your top floor radiator is simply air bound. Hop over to our radiator troubleshooting articles at RADIATORS for ROOM HEAT and you'll see how to check for and fix an air-bound heating radiator by simply opening an air bleeder.

 

Boiler won't keep pressure for more than an hour

i have a three zone ( individual circulator pumps) hydronic system that i recently changed the expansion tank and auto bleeders on and now it wont keep pressure for more than an an hour or so i have searched the system for leaks and cant see any.

i have to keep adding water to get pressure back. what else could be wrong and can i leave the make up water valve (not the pressure reducing valve) but the one that feeds it open? is this dangerous?? it is a two story house - Martin Griffin 1/15/12

Reply:

If the system is not maintaining pressure we need to look for a leak or a defective backflow preventer or check valve.

 

The relief valve at my boiler keeps leaking, even after we replaced it

My boiler has been leaking at the pressure relief valve for 1 week, with the pressure at 30-35 when hot. I drained the steel expansion tank fully, and then re-started the system. The pressure initially was back down around 20, but within 1 day was back up in the 30s and leaking at the PRV.

I had a technician come and install a new pressure reducing valve. We all thought that would fix everything.

We drained the expansion tank again before re-starting the system. After we re-started the system, the pressure continued to rise. one day later we're back at 33 PSI and draining from the PRV. I tried draining more water from the expansion tank and closing of the water valve from the city.

The pressure in the system went down to 20. After running the heat, it's now hot and at 25 psi. Could I have just gotten a defective new pressure-reducing valve? Any thoughts? Help would be appreciated. - Josh 2/7/12

Reply: things that can cause the relief valve on a boiler to leak

Great question Josh. There are actually several things that can cause the relief valve on a boiler to leak, among them is an automatic water feeder/pressure reducer that is not working properly, but there are quite a few other causes too.

The fact that you drained your expansion tank and then found that you could drain it again makes me suspect that as the best starting place.

If it's an older bladderless type expansion tank (some call these compression tanks) it may be that it wasn't adequately drained. If the expansion tank is a newer type that has an internal bladder the bladder may be damaged or the air valve may be leaking out the air charge.

Details are at EXPANSION TANKS.

At RELIEF VALVE LEAKS we provide a catalog of all causes of leaks at all types of pressure or pressure / temperature relief valves.

Also see RELIEF VALVE, TP VALVE, BOILER if your boiler is a steam boiler,

or if yours is a hydronic (hot water) system

see RELIEF VALVE, TP VALVE, STEAM BOILER

 

The water level in my steam boiler keeps rising

My sight glass on manual feed boiler rising without adding water I have steam heat system with an indirect water heater. - Anon 2/23/12

Reply:

Anonymous:

Your water feeder valve may need repair or replacement.

Review the diagnostic text in the article PRESSURE REDUCER / WATER FEED VALVE, BOILER .

This is particularly likely if the boiler water level is actually increasing.

Don't confuse increased boiler water level with surging when the steam boiler is heating up.

And don't forget to double check that someone else has not manually added water to the boiler.

The other common problem is a delay (due to clogging) in return of condensate to the steam boiler, so at the end of a heat-on cycle, condensate hasn't yet returned to the boiler so the automatic water feeder adds water; then as condensate returns the boiler becomes over-filled.

Where do I add water to my furnace

Need to know where I add water to my furnace. The low water indicator is on. Not sure where to look. And not sure if I have an automatic water feeder. Thank you LJV 109/23/11

Reply:

LJV

Indeed finding where to add water to a steam boiler can be tricky for an unfamiliar building owner because the water supply valves are not always located in the same place.

Try backing up a bit: find the cold water supply piping in your home. Follow the piping to the steam boiler.

That route will show you where water enters the boiler as the piping will end either at a manual valve, at an automatic water feeder valve, or at a combination of the two

- that is, some boilers may include an automatic water feed valve as well as a manual valve located on a piping loop that pipes around the water feed valve.

In the links listed at the ARTICLE INDEX the bottom of this article , under STEAM HEATING SYSTEMS
be sure to read the following two articles:

LOW WATER CUTOFF CONTROLS
Water Feeder Valves, Steam

Those articles include photos of the valve(s) you are looking for.

Or use the CONTACT link at the ARTICLE INDEX the bottom of this article to send me some sharp, well-lit photos of your system and I'll be glad to look them over and give more specific advice.

 

Is it ok to turn off the water supply to the heating boiler in winter?

can a hotwater boiler be operated w/out make up for 2 months during cold weather - (Sept 30, 2014) Anonymous said:

Going on vacation for 2 months and wondering if it's OK to shut the cold water supply line to the hydronic water heater.

This would still allow all the circulation etc but allows me to shut down the main water supply to our house.

This system supplies heat to our lower floor only. I would like to shut the water main off to my house while away. The hydronic heater is separate from the domestic hot water heater.

If OK then the heat would still be available but I would not have the potential problem of water leaks from the plumbing system components such as a cracked toilet tank etc.
Thanks for any comments (Nov 29, 2014) DAN D.

Reply:

It depends, Anon.

If you mean a steam boiler, almost certainly not - the risk is loss of heat or boiler melt-down or worse.

if it's a hydronic (hot water) heating boiler, maybe, if there are are no leaks. But there too if the boiler leaks it could be destroyed or cause very serious damage to the building if the boiler lose heat or explodes from loss of water.

If the boiler has a low water cutoff safety valve (as is installed on all steam boilers) then you'd hav some protection from the latter castrophe.

Dan

I sometimes shut off the water main to a home heated by a boiler but *only* if I am very confident that the system is bullet proof and leakproof - the worry is that a leak in the system can destroy the boiler or even lead to a fire.

If the boiler has a low water cutoff valve on it then you're safe: it will simply shut down if it loses water.

Otherwise I would leave water on to the boiler.

In some buildings it's possible to leave the water supply on to the boiler but to shut off all of the hot and cold water supply piping to the rest of the house. That reduces the freeze-burst-pipe damage risk substantially and is worth doing.

Dan see this recent article we put together on this at

WATER TURN OFF? - see inspectapedia.com/plumbing/Winterize_Turn_Water_Off.php

More details about this topic are at our WINTERIZE HEAT ON article found at inspectapedia.com/plumbing/Winterize_Heat_On.php

 

What valves do I need on my boiler: why do I have no heat in half of my baseboards?

I have a boiler with two spigots and two silver valves.

How do I know which one is the drain and which line the two valves go to?

The copper pipe is in a circle at the boiler and one of the handles is at the top and one is upside down on the bottom (the valve is a circular dial style handle).

I am not receiving heat to half of my base board heat.

Do I need to turn one or the other valves? How can I check it? (Nov 18, 2014) Jeqal

Reply:

Jeqal

From just your note, I don't know what valves you are referring to.

Check that each room thermostat for each heating zone is calling for heat - set the thermostat well above room temperatures.

Then check that the boiler is circulating hot water in each heating zones - touch or feel (with care) for hot pipes at each circulator or zone valve.

There could be a thermostat, zone valve, check valve, or even an air bound heating system problem.

It's time to call your heating service technician.

 

How do I know if a water feed valve or TP relief valve is bad?

How do I know the feed valve or relirf valve are bad or replace both the relief valve is letting water out. I have a new expansion tank 31 Jan 2015 Anonymous

Reply:

Anon

If you are seeing leaks from the water feeder valve chances are it needs repair or replacement; some water feeders can be repaired using a re-build kit.

But

Watch out: when you also cite that the relief valve is leaking that suggest that either the heating system is at too high a pressure or temperature (unsafe conditions that deserve a system shut-down) or the leaks could be caused by a water-hammer problem at the building or high water pressure or both.

First see RELIEF VALVE LEAKS

then

See WATER HAMMER NOISE DIAGNOSE & CURE

 

What are normal input pressures vs 40 psi on my water inlet gauge

My boiler psi reads 40 on water at the inlet gauge. Is this too high? (Feb 12, 2015) Anonymous

Reply: 40 psi house water system pressure is normal. Watch out: 40 psi at the boiler is unsafe and you'd need to shut down the heat and release boiler pressure!

40 psi is within normal building water supply service pressure ranges.

About water pressure: 40 psi on the street side of the pressure reducer/water feeder valve side of a feed valve for a boiler is ok.

Watch out: But if you are seeing 40 psi on the boiler side, such as on the boiler's gauge, something's wrong and if that's really the pressure you should shut down the system as it is unsafe.

 

I can't get water to boiler after flush-out

I shut down boiler and flushed it . When I turned it back on not getting water to boiler (Feb 24, 2015) Anonymous

Reply:

Anon

Check for a debris-clogged fill valve. Try lifting the valve bypass lever to see if that sends water to the boiler.

 

How to fix recurrent air blocked radiators, low psi water feeder

I have a issue with my 4 story building in NYC, top floor, 4floor, (2) apartments have alot of air trapped in the radiator.

I installed auto vent valves and still not helping. I force water thru the auto water feeder and that forces the air out of the line and it is fine for a few days. Then air gets trapped again.

I have to force water every 3-5 days during this winter. I believe that my water feeder psi is set at 15 psi. I don't believe it is enough pressure. Based on your input, I may need a different type of auto water feeder, more for commercial.

Every winter we have this issue and not sure what to do next.

I tried to get multiple plumbers to look into this matter and they have no idea. Based on your carlson dunlop diagram, I need 20-30 psi pressure for a 4 story building. Please advise it will be greatly appreciated. 16 March 2015 Tony

Reply:

Tony, what you say sounds reasonable to me. If you are seeing recurrent air blockage in all of the radiators of both top floor apartments that strengthens the argument.

What does your heating service company technician say about the water pressure settings?

Thank you to our readers for their generous comments

Thanks, this was really helpful as I work on my home boiler system. (Oct 27, 2014) Zach

Although this article did not help me with my specific issue, I found it to be very well written with excellent documentation. On 2011-10-23 by Joe

...

...

 

Continue reading at PRESSURE REDUCER / WATER FEED VALVE, BOILER - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• CHECK VALVES, HEATING SYSTEM
• PRESSURE REDUCER / WATER FEED VALVE, BOILER
• PRESSURE REDUCING VALVE (BOILER) CLOG REPAIR
• PRESSURE REDUCING VALVE DISASSEMBLY
• PRESSURE REDUCING VALVE REPAIR KIT
• PRESSURE REDUCING VALVE WATER FEEDER INSTALLATION
• STEAM BOILER FLOODING / SURGING REPAIR
• WATER FEEDER VALVE, STEAM If your heating system uses a steam boiler

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WATER FEEDER VALVE / PRESSURE-REDUCER FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING SYSTEMS

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