Hidden leaks in hot water heating systems, FAQs.

These articles explain how to determine that a hot water heating system is in fact leaking, and second we describe how to find the location of hidden leaks in or on heating boilers, hot water heat piping, baseboards, radiators, convectors, or radiant heat floors or ceilings.

Tips for Finding Leaks on Hot Water Boilers or in Hot Water Heating Distribution Piping

These questions and answers about tracking down the source of leaks at hydronic heating (hot water) boilers were postd originally at BOILER LEAKS, HOW TO LOCATE - you should definitely see the advice given there.

On 2018-12-17 by (mod) -how to find a hot water heating pipe leak under a slab

John

I have off and had success in locating a hot water heating pipe leak under a slab by borrowing or even buying a low priced thermal scanning device that can measure temperature over in the area.

What's the boiler up to operating temperature in the circulator running you will see a warmer area under the floor where water is leaking out of the pipe.

On 2018-12-17 by John

I have been told i have a leak in the pipes in the slab. How do i locate the leak. I see no obvious water inside or out

On 2018-12-03 by (mod) - steps in tracing a heating pipe leak under a slab

Super


Keep me posted

On 2018-12-02 by Jake

Other than the IR method I have attempted to isolate where I could and have it in the zone that heats the rear of the house however its two floors and lots of inaccessible pipe runs.

I may be able to lay my hands on some infrared gear from work, hopefully it can put an end to my weekly gurgle gurgle top up routine so as not to shock the boiler.

Thanks again

On 2018-12-02 by (mod) -

Jake

More steps for finding hidden boiler leaks.

A basic procedure to isolate leaks is to shut off input to a boiler, leave boiler off, and watch for a drop in pressure.

As you've confirmed that I'd move on to isolating whatever piping leaks possible and then repeat that test.

You might also be able to use IR infrared scanning or thermography: with the system hot and circulator(s) running, IR scanning can sometimes spot added heat spreading under a floor or area where hot water is leaking.

On 2018-12-02 by Jake

Thanks or the prompt reply.

No tankless coil or indirect water heater just a basic stand alone boiler. I think im likely fighting something that is evaporating or dripping into a crawl space (century brick home with a dirt basement) likely a combination of the two.

I would like to upgrade my boiler and go with a tankless water heater but not until I resolve the leak.

Thank you again for the response and if you have any other suggestions im all ears.

On 2018-12-02 3 by (mod) - check if there's a tankless coil

Jake,

Does this boiler use a tankless coil?

Or is it connected to an indirect fired water heater?

And unusual cases in which house water pressure is low there could be reversed leakage out of the boiler into the water system.

On 2018-12-01 by Jake - have to add water to my system every 2 weeks

Hoping I can call on you for some help, currently playing find the leak and have for several years.

I'm in a century home with a Weil McLain NG boiler (HEii), my system requires topping up every one to two weeks for optimal performance and to rid my self of the highest baseboards from gurgling when the heat cycles on.

I have checked every visible joint and repaired any that were suspect, replaced a run of pipe the previous owner had incased in concrete all to no avail.

I emptied the system and ran compressed air to see if it would whistle at the leak (system held to 20psi with no loss of pressure) and had no luck as I think its an expansion issue where a joint somewhere is opening when both heat and pressure are present.

I have no obvious stains anywhere in ceilings although some runs are under floors where I have no access to inspect. Are there any other leak detection methods you can think of that might help me locate and fix the issue without ripping up floors walls and ceilings.

Any additional help would be most welcome.

Thank you for your time.

On 2018-09-26 by (mod) - water feeder valve failure

Robert,

IF your boiler has an automatic water feeder/pressure reducer valve it is possible that it has failed internally - I have encountered that exact situation. IN that case the valve may simply refuse to feed water to the boiler.

Separately,
IF you are filling the boiler manually, when the boiler is off and cold you should see 12 psi pressure - more if the building is more than 2 or 3 floors in height.

Once adding water to a hydronic boiler (this is NOT true for steam boilers) you should not have to keep adding water. If you do there is a leak somewhere to be found and fixed - in the boiler or piping or radiators or baseboards.

Please review PRESSURE & TEMPERATURE SETTINGS, CONTROLS

At PRESSURE REDUCING VALVE DISASSEMBLY you can see examples of what clogs and prevents an automatic feed valve from working - which is why manufacturers don't claim it's an automatic water feeder.

On 2018-09-26 by Robert

Hi! Thanks for the reply. The gauge does go up when the boiler is hot. I have to manually fill the boiler with water so how would I get it to have cold pressure? It's weird. Like I said, the boiler actually works pretty good. Especially now with the flush and refill. I am starting to think the "if it ain't broke" philosophy applies here. Hehe.

Another question if you might know... The lines that go to my baseboards have two parts at the origination point from the boiler. I have no idea what these are. I have sent pictures to boiler companies etc and no one has yet been able to identify them for me. If I attach a photo would you be willing to give it a shot?

Thanks again! :)

On 2018-09-21 16:41:55.475490 by (mod) -

Robert

I may be missing something here but normally a residential hot water heating boiler system will show at least 12 psi when the boiler is cold.

Start by finding out if your pressure gauge is working - does it change (go up) when the boiler is hot? IF not, replace it.

On 2018-09-21 16:26:48.016324 by Robert

Hello! I have a 70's model Slant-Fin Galaxy GG Hot Water Boiler. It works pretty good and I just had a "professional" help me flush the system and refill it. He swore that the circulation pump needed to be switched around. Well... a few days after he left I decided to check pressures etc...

the pump wouldn't work. It was sucking air. So... I switched it back the way it was and topped everything off and

voila... the pump worked again. Here is my dilema... I don't show any cold water pressure at all. (I have a closed system...

I have to manually add water if needed) The hot pressure seems to be fine. Should I worry that I don't have any cold pressure on a system like this? I wanted to just replace this thing (and I still might), but I was told that these cast iron heat exchanger boilers will almost last a lifetime and there's no sense in replacing it.

Would sure be happy to chat back and forth about this if someone would be willing to help. I can provide pictures etc. Thanks so much. What a great site with lots of great input. Regards.

On 2018-06-02 18:34:35.043289 by (mod) -

You're right that are in the heating pipes could be a sign of a leak somewhere in the system. I could also be, however, that the air eliminators are not working.

You should ask your heating service person to inspect the system for leaks and also to make sure that all of your automatic air purging devices are working.

On 2018-06-02 18:06:57.545525 by Mary

I had new carpet installed in my baseboard boiler heat rental house last year. I suspect a small leak because when the boiler kicks on it sounds like water is running through the heating pipes until they are heated up. I don’t remember it doing that before.

Will I have to have the entire system replaced or can a small leak be repaired. The pipes are incased in these thin aluminum “slats” that I assume help radiate the heat. The slats are about every quarter inch or so

On 2017-04-14 5 by (mod) - leaks under the slab

CP

Your question includes some good diagnostic clues. I suspect that there is a leak somewhere - as do you.

Under a slab a small leak could let water out into the soil. You might spot this, depending on piping routing, by borrowing or hiring someone who has a good infra-red IR scanner or imager; often a leak in an under-slab hot water pipe will show up as a wide blossoming area in the IR image.

Your pressure gauge idea would work too but that'll mean of course taking the time to cut the lines, install the gauge, shutoff valves, then bleed all air, then restore the system to operating pressure. If you run the troublesome zone up to full heating temperature you'll probably have 30 psi in the line - that ought to be enough to find a leak.

Before going to that trouble I'd fix that circulator drip: air can enter the heating zone elsewhere, such as at a bad circulator pump gasket.

Usually those leak "out" but I've had some heating techs insist that the suction side of the circulator can sometimes also draw air in at the same point. Your drip is a good clue. And it's probably not a costly repair.

On 2017-04-14 by CP

I have a commercial boiler with 14 heating lines going to and from it and connected to an indirect hot water tank.

The issue is that only one of the 14 heating lines needs to be bled every two weeks or so, specifically when warm days stop the circulation of heat thru any of the 14 heating lines, sometime thereafter I need to bleed that one line.

All the heating lines, including the problematic one, travel under a slab as they make their way to the apartment and on the return. I have not seen any puddles anywhere where the lines go or any ceiling or wall leaks (rust, etc...).

I was thinking of closing the valves at both ends of the heating line and then putting a pressure gauge on the boiler drain valve of the return line.

If it dropped in 24-48 hours I would know there is a leak, but I may not know exactly where...

Should I pressurize the line to force the leak if the pressure drops? One other point is when the heat circulator is off a boiler pipe joint drips (1 1/2 inch pipe), not sure of this could be a factor or not, I'm thinking not for just one of 14 heating lines. Any advice on how to diagnose?

On 2017-03-27 by nipesh

Please given idea in side boiler after down, how to find there The leak is where and Which are tube leakages because many tubes in side the boiler,our general practice is tubes plucking/if any pinhole their so close by welding, but how to find the leakage, if available any equipment’s, please reply

On 2017-01-30 - by (mod) - chemicals to seal pinhole leaks in boiler piping

Don:

Please see CHEMICAL TREATMENTS, BOILER

Watch out: if corrosive boiler water has thinned the copper piping the pinhole leak you see and fix may be just the proverbial tip of the leaky iceberg. Expect more trouble until pipes are replaced and boiler water corrosivity corrected

On 2017-01-30 by Don B

Has anyone used an additive in a closed hydronic system to seal a pinhole leak in copper pipe?

The boiler holds pressure but the return side before circulating pump loses pressure when zone valves close, it takes approximately 10 minutes. I cannot find any evidence of water leaking anywhere.

On 2016-12-21 by (mod) -

Search InspectApedia for Well Water Piping Leak Symptoms, Diagnosis, & Repair Methods

On 2016-12-21 14:29:40.885224 by كشف تسربات المياه

Great service but give me some information about underground water leak detection.

http://alarabya.co

On 2015-11-25 18:09:56.967624 by (mod) -

Anon:

The leak is where - in a water line?

Watch out: since such pinhole leaks normally occur by corrosion from the inside, the damage is worse than you see from the pipe exterior.

You can make an emergency, temporary repair by cleaning the pipe surface and installing a clamp-around pipe leak repair device - typically it includes a rubber gasket that presses over the opening. Epoxy repairs are tougher since you'd have to stop the leak first.

There are however some fast-setting press-and-hold expoxy products that can stop a low pressure leak in the pipe.

For a safe reliable repair you will want to replace the damaged pipe section.

On 2015-11-25 15:18:48.214252 by Anonymous

How do I plug a water leak the size of a pinhole leading into my oil heating burner

Question:

Nov 2, 2012) Anonymous said:
This year we keep having banging in the pipes and we are still bleading air out of the system. We have heat but also have noise. Our system is 27 years old. We are looking for things to look for?

Reply:

(Jan 13, 2013) Anonymous said:
You have a rupture diaphragm in your expansion tank so it is filled with water and no longer has an air cushion to dampen system. Be prepared to get wet- have everything ready when changing.

Moderator said:

It sounds as if you have not found the cause of air leaks into the system or have not adequately bled air out of the system.

See AIR-BOUND HEATING SYSTEMS - home

Then

See BANGING HEATING PIPES RADIATORS

Question: steam boiler leak, can't find the crack.

(Jan 22, 2014) nathan said:
my gas steam boiler is leaking lots of water and don't know how to locate probable crack in the boiler. At first it was the piping, which I fixed. Please help

Reply:

Nathan, there are som additives that claim to stop boiler leaks but I'm doubtful. Typically the tech will remove the boiler jackets or covers and inspect to see if it is a repairable leak or not.

Is this a steel or a cast iron boiler?

Watch out, never pick at corrosion or you may turn a slow leak into an immediate catastrophe.

Question: water coming out of boielr side

(Mar 9, 2014) Anonymous said:
I have a oil beckett oil heater Model S-165-AP it has water starting to come out the bottom on right side of heater. no water came out any values. can it be fixed/

Reply:

Anon:

There are leak-stop products that can be added to some boilers that may stop a leak, though not without risk of clogging circulator pumps, zone valves, controls; IMO the success depends on the nature of the leak - a crack vs. a rust-perforation, as well as other factors. Though its costly, welding has been used on occasion too.

I would let the heating tech take a closer look at the boiler - removing jackets to determine the location and nature of the leak;

If the leak is not at a fitting or tapping but rather in the body of the boiler itself, especially from rust, it's probably time for a new boiler.

Question: leaks at new boiler installation

(Apr 22, 2014) Anonymous said:
I have a brand new hydronic air conditioning unit in my attic. I had the air on set at 76 for the past two weeks. Water started coming thru my ceiling from the unit leaking.

The air filter is new so I can't figure out why a new system would leak so much water. I can see it is coming from inside the unit.

izza bella said:
I too have installed my hot water boiler from a Boiler in Brooklyn but after two three months its starts leaking. But when i called them they said just turn off and tighten it.

Reply:

Anon, it sounds as if the AC condensate is leaking - your service tech needs to open the unit, check the condensate drain system, etc.

Izza

Tightening something may be all that's needed to stop a leak - or it may not.

All depends on the where and why of the leak.

It also depends on how long the leak has been going on: a longer leak risks corrosion of the surfaces over which water is passing or mineral deposits, either of which can make it tough to stop the leak without shutting down the system, disassembling parts, cleaning surfaces, installing new gaskets and where appropriate, using an appropriate gasket sealer.

Since some leaks could imply unsafe conditions (such as spilling from a temperature-pressure relief valve), you should have a trained HVAC technician inspect and repair the system.

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Recommended Articles

• BOILER LEAKS CORROSION STAINS
  • BOILER LEAKS, HOW TO LOCATE
  • CHEMICAL TREATMENTS, BOILER
  • HEATING BOILER LEAKS, INTERNAL

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