Check valves & flow control valves on hot water heating systems:

This article explains types of check valves used on hot water heating systems.

This article series answers most questions about Heating System Boiler Controls on central heating systems to aid in troubleshooting, inspection, diagnosis, and repairs.

Q&A on Check Valves on Hot Water Hydronic Heating Systems

These questions & answers about heating boiler check valves, also referred to as flow control valves, flo-control valves, and similar valves used on hot water heating systems were posted originally at CHECK VALVES, HEATING SYSTEM - be sure you review that article.

On 2020-02-19 - by (mod) - solving the un-wanted heat problem: look for a bad check valve

Erica

You should not need an additional valve to solve the "un-asked-for heat" problem.

That is to say there should already be flow-control valves or check valves installed for each of your heating zones, OR individual zone control valve.

So your heating service tech should be looking for a check valve or flow control valve that is either stuck open or improperly set.

That might be a zone control valve or a Flow-Control valve like the red B&G Flow-Control valve shown at the top of this page.

On 2020-02-19 by Erica

Hi- I recently moved into a new home with 5 zone heating, I am by no means a pro.

After changing to a programable thermostat for one of the heat zones, I noticed at least one of the zones get what I think is “ghost flow” and maintains a higher temperature than its setting overnight. It seems to get hot when some of the other zones are on.

I am wondering if having someone install a control flow valve near the returns would solve my issue? Any thoughts are appreciated, I added pictures below.

On 2019-11-25 - by (mod) -

Click the

Show References

Link
at the bottom of CHECK VALVES, HEATING SYSTEM where you will see installation instructions for several models of flow control or check valves.

There you will see that when the valve is used in the position shown in your photo the end that we think is connected to your expansion tank supposed to have been plugged.

The result of that may be that the expansion tank is simply out of wrong location where it's not effective

that in turn would cause water to spill at the relief and it would cause the heating system to use water.

On 2019-11-25 by nguyen

and shown just above is a photo of how connections are made at the B&G flo control valve.

we hire contractor convert oil water heater and tank-less hot water to gas water heater and tank hot water 4 years ago. i suspect that the expansion tank is at wrong location

On 2019-11-20 - by (mod) -

I am not sure, Nguyen.

Please post a photo - one per comment - or several to show the equipment and its piping and the expansion tank; when we can see the setup I may be able to comment more usefully.

On 2019-11-20 by nguyen

my water heater have B&G flo control valve: 1. bottom connector connect to boiler, 2 left connector connect to expansion tank, 3 right connector connect to pipe to radiator. is expansion tank at the right place? my boiler is only for heat.

On 2019-11-07 - by (mod) - Can a Bell and Gossett valves be adjusted by stretching the spring

Bob:

For the typical B&G Flo-Control valve like the one shown here, you'll see that there is no internal spring; if your valve has a spring I'd like to know the valve model and to see a photo of it.

There IS a spring inside of some other B&G parts such as the company's pressure-reducing valves. That spring is adjustable by a locknut & turn-screw.

Watch out: But in any event stretching the spring is in my opinion a bad idea: you're modifying the manufacturer's part in a way that risks any of several failures including leaks or failure to operate as a check valve as it should

On 2019-11-07 by Bob

Can a bell and Gossett valves be adjusted by stretching the spring I want

On 2018-07-23 - by (mod) -

Yes, Greg,

Install point of use water temperature regulating valves at each shampoo station. Then assure that the hot water source has sufficient temperature and volume to feed all three.

On 2018-07-22 by Greg

My wife has a business with three shampoo stations feeding off one hot water line. Is there a way to regulate the hot /cold water supply so that it does not cause an outlet being used to change temperature significantly when a second or third is turned on?

On 2018-07-23 by (mod) - how to regulate hot water temperature at fixtures

Yes, Greg,

Install point of use water temperature regulating valves at each shampoo station. Then assure that the hot water source has sufficient temperature and volume to feed all three.

See ANTI SCALD VALVES for details

On 2018-07-22 by Greg

My wife has a business with three shampoo stations feeding off one hot water line.

Is there a way to regulate the hot /cold water supply so that it does not cause an outlet being used to change temperature significantly when a second or third is turned on?

On 2018-01-03 by (mod) - if a check valve is stuck closed

Yes, possibly, but other causes such as an Airbound heating system or problem with the circulator pump are more common

On 2018-01-0 by mark

if a check valve is stuck closed will it prevent the hot water from circulating even though my circulator runs.

On 2017-10-19 by Peter

I have three zones with cast iron style check valve. I usually have to tap on them to get them to close. My new furnace guy turned the top screws all the way down while I had them all the way up. Now my furnace only clicks on for hot water. Not when it calls for heat. Any idea?

On 2017-02-06 by Debra

My heat is good but the house is old
1914 was built..used to heat with oil. now it's Converted to gas using the oil

Old oil Burner ..I guess that's what they told me..but I have seen Blk specks in the water at first turning hot water on..I have a good sense of smell and I smell the house when the heat first comes on a truck oil Garage like smell and I seem to be the only one that notice's it.

I was told that's just old rust from the old boiler.I thought it might be oil in the water or rust it's that kind of smell also.

I'm worried that is why I haven't been feeling well for a few yrs.. once summer comes I don't smell it.. heat's off but hot water heater is running..
anything I should be worried about..I don't understand what is happening but I'm a transplant survivor and I don't want any other problems..
Thank you
Sincerely Debra

On 2017-02-02 by Curt

Asked about taco 219 flo-chek (really says 219 swetchek), can't find where I asked question, I opened and closed knob on top a couple of times and it is working correctly again

On 2017-01-30 by Alfred Edgmon. edgmon9033@yahoo.com

I have a hydronic system heater works fine hot water heater is new but i can not get hot water to the facets i think it may be the check valve can a bad check valve allow cold water into system and dilute hot water headed to facets

On 2016-12-01 by (mod) - contact information for Taco

Mitch:

A Tasco Flo-Chek valve is normally installed above the heating boiler on the hot water line exiting the boiler. For other applications or positions I'd check with Taco directly, as in the product literature there is no discussion of position or other installation details.

Taco Comfort Solutions, Inc.
1160 Cranston St.
Cranston, RI 02920
Phone: (401) 942-8000
FAX: (401) 942-2360
E-Mail: Customer Service

Taco (Canada) Ltd.
8450 Lawson Road
Unit # 3
Milton, Ontario L9T 0J8
CANADA
Phone: (905) 564-9422
FAX: (905) 564-9436
http://www.taco-hvac.com/ the company's Contact page permits emailing a question

Here is how Taco describes their Flow Control Check Valves:
Taco Flo-Cheks prevent “gravity” circulation in forced hot water heating systems during periods when the boiler is hot, but the space heating zone is not wanted.

This makes it possible to use the heating boiler to maintain domestic hot water year-round. You can also use Flo-Cheks in systems with multiple circulator zones to allow heat to flow only into the zones that are calling for heat.

In addition, the thumb screw can be opened manually for gravity feed applications, if the main circulator stops operating. 125 PSI maximum operating pressure (862 kPa) and 277° F maximum operating temperature (136° C).

On 2016-12-01 by Mitch

How to connect a taco in line check valve for hot water heating

On 2016-03-21 by (mod) -

Joe:

One of the causes of this problem is discussed in the article above - a stuck-open check valve.

If your boiler itself is running, check for thermostat wires that are shorted together.

On 2016-03-21 by joe

my baseboard heat keep running even though i have the thermostat off

On 2016-03-03 by (mod) -

Water will flow by natural convection up if it's hot, or possibly down into the boiler if it's cold. It sounds as if your faulty flo-control valve(s) need(s) replacement

On 2016-03-03 by Tom -

AUTHOR:tom (no email)
COMMENT:I have three flow check valves off my basement furnace.

Once in a while one of the upstairs zones sticks and the hot water flows and the heat is higher than the set point. Tap the valve and it closes.If the basement flow check were to stick open the heaters are at a lower level than the boiler. The hot water could not flow downhill and thru the system as it would in the upper zones. Am I correct? My furnace guy tells me it can. Please tell me who is right. Thanks.

On 2016-02-03 by Mary

Have a valve on the return pipe coming off thr water heater Waterheater is working changed the circulating motor and still not getting hot water in house could vale be stuck on swinging check valve the new circulating motor is getting hoy

On 2016-01-26 by Juan Carlos

Maybe I'm not finding it, or I'm just not understanding what I'm reading. I have two zones, one keeps getting heat even when it isn't calling for heat. How can I separete the two zones?
I have two circulators, one for the upstairs zone and one for the downstairs zone, but the one for the downstairs is at the return pipe for the water, can that be why the upstairs gets heat when the downstairs ask for heat?
I guess the better question is, where if anywhere should I put an flow control valve to keep the downstairs from hearing the upstairs?
Thank you in advance!
Juan Carlos

On 2015-11-26 by (mod) -

Pedro:

I'm not sure what control valve you mean - please use the page bottom CONTACT link to send me photos of the valve, its location, and any tags or markings.

If you refer to a flow control valve such as those shown in the article above, it is true that SOME circulator pumps may contain their own built-in check valve. Most older pumps don't. You need the valve to prevent hot water circulating by convection when you're not calling for heat.

On 2015-11-24 by Pedro C

Have an old b &g control valve on boiler. I believe it's stuck. Have circulating pump (taco) on return side just in front of boiler. Guy I called took a look and said that you don't really need control valve and to remove not replace. Said it was put in place before the circulating pump and not needed. Any thoughts. ?

Reader comments:

(July 13, 2012) Toni Bands said:

Thanks. I've had a problem with backflow from the hot water system, even when the water mains are turned off and your article is very explicit and clearly shows what should be done to correct the problem.

(Jan 28, 2013) Pete D. said:

Tons of valuable, detailed, clearly explained info with pics and diagrams. Thanks much. You answered about 10 questions i had with this article.

(Dec 8, 2014) Anonymous said:

This whole site is one hell of a good idea.....awsome.

Reply:

Thanks so much, Anon. We work hard on the information to make it useful and accurate; compliments are great compensation We also welcome criticism, questions, content suggestions. - Ed

Question:

(Mar 23, 2013) AD said:

\i would like to know how is a flow switch wired in a hot water boiler

Reply:

AD I'll research and answer your question - but from what you asked I don't understand enough to even hazard a guess. What kind of flow switch, intended for what purpose? Can you give me a product name and part number?

Question:

(Feb 4, 2014) Billy said:

I haven oil fired boiler for hot water baseboard heating and hot water for showers and sinks. Even when the thermostat is off, the boiler will fire up to keep the water temp and pressure constant. Is this normal?

Reply:

Yes, Billy, if your heating boiler uses a tankless coil to make hot water for washing and bathing, even when the thermostat is not calling for heat the boiler will keep itself hot in order to heat domestic hot water passing through the coil. Search InspectApedia for

TANKLESS COILS

to read details.

Question:

(Feb 24, 2014) Lynn Zimmerman said:

I have a hot water boiler that is heated by multifuel and solar. When heated by solar (mainly in warm months) heat rises by convection to the zones through the return pipes. Can a check valve be used to prevent this and what type would work best? The location would be vertical mounted.

Reply:

Lynn what you suggest sounds right to me. The check valves discussed in the article above are performing that same function for fossil-fuel heated water, preventing water in the boiler from rising by convection up into the building baseboards or radiators, but opening and permitting water to flow in response to the pressure difference created when the circulator starts.

There are other concerns about solar systems and possible overheating of other system components that mean you'll want to review the design with the solar manufacturer.

Question: water feed valve causes backflow preventer leak?

(July 8, 2014) Edward Martin said:

Could a defective automatic water feeder valve cause backflow preventer valve to leak at the Vent side of the "T"

Reply:

Edward,

Some discharge from a backflow preventer is normal, such as if water pressure on the supply side falls to atmospheric pressure.

Other periodic discharge from the backflow preventer, showing up at its vent tube, can be caused by a water hammer problem in the building. To diagnose water hammer troubles see

inspectapedia.com/plumbing/Water_Hammer_Noise.php

If the backflow preventer is dripping constantly there is probably dirt on its moving check valve parts (internally) - a condition that can be corrected by cleaning the valve or by replacing it.

Also check that your backflow preventer is properly installed and located - on the fresh water feed line but *before* the pressure regulator.

Question: heat won't shut off

(Nov 24, 2014) Brian said:

I have a boiler zoned for 3 areas, regions, and even though I have one thermostat turned low the heat continues into that region. I believe this is the safety, the Bell shaped type, is there any other way to check and verify?

Reply:

Brian, if you disconnect the thermostat wires from the zone valve or circulator relay and still have heat in that area I suspect the zone valve is stuck open, or a flow control valve is stuck open or is set in the Manually-Open position.

Question: change oil fired boiler over to natural gas?

(Dec 7, 2014) Merlin Strom said:

I have a 20 year old Burnham hot water boiler fuel oil fired. I would like to change it to natural gas. would it be beneficial to only do the burner or better to change out the complete boiler.

Reply:

Merlin I'd be a bit surprised if your heating service company would consider a complete fuel swap - though it is probably technically possible the amount of labor and parts, considering also the age of the boiler, would argue for a new gas fired boiler already complete, assembled, and properly done.

Comment:

(Dec 20, 2014) Ryan said:
Thank you, Don, for your help. I am taking everything in to consideration. It may even be a clog in the water tak itself. Still working. Have a Merry Christmas and a safe New Year.

Question: no heat upstairs - trouble bleeding baseboards

(Jan 6, 2015) BrigitteIsCold said:
I have a question, last year no heat on 2nd floor, so got a friend to show me how to bleed the air out of the baseboards. This year however, I am hearing a lot of gurgling in the pipes, and have been taking the air out of the 2nd floor baseboards 2-5 times a day.

sometimes water spits out, sometimes it just lets air out. Its been a month of taking air out. How much air is in these pipes, how does the air get there? Could there just not be water getting in? I never touch any of the valves so nothing should be 'off'. Any help would be appreciated.

Reply:

Brigitte

It is possible that air has simply not been adequately removed from the system - it can be difficult to get air out of long horizontal piping runs using just air bleeders at baseboards.

See AIR-BOUND HEATING SYSTEMS - for details about the various ways to get air out of the heating system.

It's also possible that there is a piping leak and air is entering piping when the heating system cools down but that's less likely. For example when a hot water heating system cools and pressures in the system fall it is possible to see even a vacuum in higher baseboards or radiators in the system. Also there is some air entrained in water that returns to a gas state when water is heated.

Question: what temperatures should I see at the "furnace" (boiler?)

(Jan 28, 2015) Anonymous said:
at what temperature should the furnace be at during cold winter months?

Reply:

Hot water type (hydronic) heating boilers typically run up to about 180 to 200 degF. depending on how the aquastat is set.
See
AQUASTAT CONTROLS

Furnaces (forced warm air heating systems) run in the range described by the fan limit switch
- see
FAN LIMIT CONTROL SETTINGS

Question:

(Feb 19, 2015) PAUL said:

Boiler gravity flows w/the circulators disconnented'i have also chanded both flow check valves and lowered the pressure to approx 3-5 pounds still hot water flows

Reply:

Paul

Check that the flow control valves are installed in the right direction and their controls in the Winter. Direction.

See CHECK VALVES, HEATING SYSTEM

Question: Only one side of heating valve gets hot

Oct 14, 2015) Joe said:
Only one side of heating valve gets hot

Reply:

Joe

Then the flo-control valve is either stuck closed or has been manually placed in closed position.

Question: Is a control valve needed with single zone/circulator to prevent gravity circulation?

2015 10 25 Tom said:
Is a control valve needed with single zone/circulator to prevent gravity circulation??

I Had my New Yorker/Beckett Oil furnace with domestic hot water loop, 2 forked zones on single circulator replaced with another New Yorker last month. Flow between forks/floors is adjusted with a small inline restrictor valve.

The house temp is getting over 85 degrees, but the circulator is not running / thermostat off. I'm guessing it's "gravity circulation" since the new heater does not have a flow control valve installed. The old setup did have a valve. Is a flow control valve necessary with just a single circulator pump? Can there be gravity circulation with a circulator pump in line?

Reply:

Yes, Tom. Though some circulator assemblies may contain their own check valve or flow-control valve. Tell us the brand and model you have and we can help look that up.

...

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