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Radiator leak (C) Daniel Friedman Guide to Finding & Fixing Leaks in Heating Radiators, Baseboards & Convectors

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Heating radiator leak troubleshooting:

This article describes how to find and fix leaks in hot water heating radiators.

This article series answers most questions about all types of heating systems and gives important inspection, safety, and repair advice. In addition to cast iron radiators using hot water or steam as a heat source, we describe two other very common hot water heat distribution methods below.



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Where to Check for Leaks on Baseboards, Radiators, or Heating Convectors

Heating baseboard leak (C) Daniel Friedman

Here we describe the types and locations of leaks found on heating radiators: hot water, steam, cast iron, heat convectors, basn radiators, between abutting radiator sections near the bottom of the unit.

Article Contents:

Common leak locations on baseboard heating systems

Obviously, first look at the floor around each heating component to see if you see water stains or water damage. (Water damage can occur at steam radiators too, as condensate could be leaking at the condensate return pipe fittings.)

If you don't know what kind of heat your building uses, we explain how to figure out the answer at HEATING SYSTEM TYPES.

If your heating system is not working properly, see NO HEAT - BOILER or NO HEAT - FURNACE.

Heating baseboard leak (C) Daniel FriedmanOn heating systems using hot water baseboards, leaks can occur anywhere in the piping system, including at air bleeders located at the ends of baseboard sections, at couplings or elbows in the piping system, or where freezing has cracked or burst a heating baseboard pipe.

Our photo of a leaky heating baseboard (above left) shows that prolonged leaks may rot carpeting (leaving an obvious leak clue once someone vacuums up the ruined carpet at this spot) and may also cause hidden damage to the subfloor or even the structure. Or perhaps a mold problem may result.

Our baseboard piping leak photo (above right) shows how freezing pipes may cause separation at a solder joint instead of actually bursting the piping. In the case shown, the original solder joint had been poorly made, so this was a weak point that broke first.

Leaks at heating baseboard air bleed valves are shown at AIR BLEEDER VALVES. If your heating baseboards are not in fact getting warm when your thermostat is calling for heat and the boiler is indeed running, see AIRBOUND HEAT SYSTEM REPAIR

Also see WINTERIZE A BUILDING for examples of freeze-burst copper forced hot water heating piping in a baseboard heat system.

Question: repair a pinhole leak in copper baseboard

I'm a journeyman plumber and I know how to braze but I'm not sure how to go about repairing a pinhole leak in a copper hot water baseboard heater. Obviously it has to be dry before I can braze it but how do I drain it and once repaired how do I properly fill it up with water and bleed the excess air?

Reply: solder repairs of small leaks in copper heating baseboard piping

The proper repair of a pinhole leak in copper piping would be soldering not brazing. But you'll most likely need to remove the water from the baseboard heater first. Or one can cut out a bad section of tubing or piping and solder in a short section with unions and copper piping of the same diameter. Be sure to properly sand and prep the copper pipe surfaces, remove any burs, and use a soldering paste or flux to assure a good solder connection.

Watch out: often the presence of a single pinhole leak is an indicator of more trouble ahead. Corrosion, or too-thin or defective copper piping may be prone to developing multiple leaks. I'd go ahead and patch or repair the present leak, but I'd keep an eye on the building heating distribution piping and baseboards for more leaks down the road.

Also see CHEMICAL TREATMENTS, BOILER where we include a discussion of leak-stop products for hot water heating boilers & steam boilers.

Question: leak at copper sweated elbow at radiator - can I use epoxy?

(Feb 13, 2014) sid jones said:
there is a leak after sweating a copper elbow to my hot water baseboard radiator
would epoxy be ok as an emergency fit?

Reply:

Sure, Sid , you will have temporary success if you can get the joint clean and dry long enough to bond. Try an automotive radiator repair epoxy intended to tolerate heat. Keep an eye on the patch lest it leak unattended.

Common Leaks in Cast Iron Hot Water or Steam Radiators

Leaks occur between sections of cast iron hot water or steam radiators.

Splits and leaks in a cast iron radiator (C) Daniel Friedman

The radiator may leak where sections of cast iron are bolted together, or if the radiator has rusted-through or become cracked, perhaps by freezing, you may see rust and leak stains at splits in the individual radiator sections (photo below).

Leaky steam radiator (C) Daniel Friedman

While an individual, accessible crack in a cast iron radiator might submit to an epoxy repair, extensive damage such as we show above usually means the heating radiator should be replaced.

Radiator leak (C) Daniel Friedman

Sometimes a leak at a steam radiator is not critical - you may at least make it through the heating season, or the leaking may occur only when the radiator is cold (photo, above-right, also shown at page top, of a leaky steam radiator). This is a steam condensate leak.

Radiator valve leaks (C) Carson Dunlop Associates

If you see rust stains and leak indications between radiator sections at the top of the radiator, such as in our photo (above-left), or other rust, splits, or evidence of leakage from the body of the radiator, we recommend that you ask for repair advice from your heating service company.

Leaks also occur at radiator valves, at radiator bleed valves, and at the piping fittings where valves and pipes join the radiator bottom or top.

As Carson Dunlop's sketch (left) warns, watch out for hidden structural damage or damaged ceilings below leaky radiator valves.

Question: are steam radiator leaks dangerous?

Josh asked: I have an old one pipe steam radiator that has a small crack about 8 inches up. It drips a bit but my concern is the steam. Is this dangerous to have expelled into the air as far as breathing quality. I am not sure If it is a health issue. I have some concerns about having It replaced with a cheap one from china.

Thanks so much for your help. - Josh (also by email) J.F. Thank you so much for your help.

R  said: Today at work, a few pipes and radiators blew in some of the rooms. The leak and steam got so bad you could hardly see your hand held out in front of your face.

I was in there for a while trying to find the shut off for the water and keeping the water from leaking out into the hall. I was breathing all that steam in for quite some time and I was wondering if there is anything I should be worried about. My lungs and eyes were a little irritated, but I am wondering if there could be something more. - R. 1/30/2014

Reply:

Josh

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with leaky radiators, including possible hidden damage from prior or long-standing leaks.

That said, here are some things to consider:

Follow-up comment: Harmful chemicals in steam from steam boilers?

Thanks for the quick reply Daniel. I was unsure if chemicals were commonly used in the w

Reply to R about steam radiator leaks & chemical exposure:

While residential and most commercial steam systems operate at very low pressure - under 1 psi, there are some commercial systems that work at higher numbers - where an actual explosion would be potentially dangerous.

I am GUESSING that you are talking about a low pressure steam system and a failure of one or more steam vents on radiators - or an actual burst steam pipe.

The immediate dangers would be steam burns, or if vision is obscured, other obvious hazards like not being able to see to get safely out of the building.

Past those immediate worries, you will want to find out what boiler additive chemicals were being used in the steam system in your building, then to look at the MSDS exposure guidelines for those products. Without that data, an immediate answer to your question would be just speculation.

As I note in the article above,

Check with your boiler service company and take a look at the boiler service tag - let me know if any additives were used in your system (unlikely in residential steam boilers) and we can research further by reviewing the MSDS for those products.

Corrosive liquids used in some treatment compounds are skin, lung, and eye irritants (and considered unlikely to be ingested), but you would not expect to find these being released at harmful levels into occupied space from a steam radiator steam leak, since the same steam is also vented quite normally through steam radiator vents during normal system operation.

Let us know what chemicals were in use and if needed I'll be glad to do some further research.

With any chemical, even distilled water, the poison is in the dose.

Question: Can I fix a cracked heating radiator

(Oct 20, 2012) Rich Jankowski said:

i have a hot water heater and get heat thru a water baseboard heater .
There is a crack in the heater and water leaks out .Can it be sealed or will it need to be replace ?

Reply:

There are stop-leak products as well as epoxy sealers that MIGHT form a temporary repair and may require application on a cool dry surface, but I'd worry about the repair not being durable.

Please see CHEMICAL TREATMENTS, BOILER where we include a discussion of leak-stop products for hot water heating boilers & steam boilers, including boiler treatment products & MSDS information

Question: pipes and radiators blew up and released steam

(Jan 30, 2014) R said:

Today at work, a few pipes and radiators blew in some of the rooms. The leak and steam got so bad you could hardly see your hand held out in front of your face. I was in there for a while trying to find the shut off for the water and keeping the water from leaking out into the hall.

I was breathing all that steam in for quite some time and I was wondering if there is anything I should be worried about. My lungs and eyes were a little irritated, but I am wondering if there could be something more.

Reply:

R,

Ugh what a mess.
While residential and most commercial steam systems operate at very low pressure - under 1 psi, there are some commercial systems that work at higher numbers - where an actual explosion would be potentially dangerous.

I am GUESSING that you are talking about a low pressure steam system and a failure of one or more steam vents on radiators - or an actual burst steam pipe.

The immediate dangers would be steam burns, or if vision is obscured, other obvious hazards like not being able to see to get safely out of the building.

Past those immediate worries, you will want to find out what boiler additive chemicals were being used in the steam system in your building, then to look at the MSDS exposure guidelines for those products. Without that data, an immediate answer to your question would be just speculation.

As I note in the article above,

Check with your boiler service company and take a look at the boiler service tag - let me know if any additives were used in your system (unlikely in residential steam boilers) and we can research further by reviewing the MSDS for those products.

Corrosive liquids used in some treatment compounds are skin, lung, and eye irritants (and considered unlikely to be ingested), but you would not expect to find these being released at harmful levels into occupied space from a steam radiator steam leak, since the same steam is also vented quite normally through steam radiator vents during normal system operation.

Let us know what chemicals were in use and if needed I'll be glad to do some further research.

With any chemical, even distilled water, the poison is in the dose.

Leaks in Steel Heating Radiators

Steel heat sink or night storage radiator on a Scottish biomass boiler hot water heating system - leak is circled in red (C) InspectApedia.com 2016

The steel radiatior shown above and in more detail below is the heat sink radiator for a hydronic heating system in Scotland that uses a biomass boiler that burns wood pellets. The radiatior is connected to a lagged hot water tank. Other radiators in the home are controlled by thermostatic radiator valves. This radiator is developing a rust perforation leak (circled in red).

[Click to enlarge any image]

Steel water-filled radiators are widely used as heat sinks in systems that store heat during off-use periods to return it when needed or to absorb extra heating capacity to provide more even heat distribution in a building. In New Zealand and some other countries, similar steel-constructed night storage heaters may be oil-filled and operate on electricity, accepting and storing heat during off-peak electricity-use hours. See NIGHT STORAGE HEATERS & HEAT SINK RADIATORS.

Leak in steel heating radiator (C) InspectApedia MC

Question: small bubble on bathroom radiator is leaking water

A small bubble has appeared on our bathroom radiator and it is leaking water when the radiator is cold and leaving a rusty streak. It's been in place for a number of years and I have no knowledge of it being damaged.

You've already suggested using epoxy resin to seal it, which I will look into. However, will I most likely need to replace the radiator in the near future? - Anonymous by private email 2016/06/21

Leak in steel heating radiator (C) InspectApedia MC

Reply:

Good photos, bad kind of leak in that the area around the leak is probably thin and fragile.

Watch out: DO NOT TOUCH THIS LEAKY SPOT, because from your photo it looks as if this is a steel radiator not a cast iron unit. If I'm right, then in that case the walls are pretty thin. Steel corrodes from the inside of the radiator outwards, so the area around that leak is pretty thin. So poking around is likely to make the small leak into a big one immediately.

If you can turn off the radiator I'd do so, as I worry that the leak may worsen when you're not at home.

In an emergency you could epoxy or tape a patch to the radiator surface around the leak but I don't trust the repair: the adhesive is bonding only to paint on steel.

Other Questions about Radiator Leaks

Question: ammonia odor and possible radiator leaks?

(Feb 27, 2012) Thank you said:
There has been a sharp ammonia like odor in my apartment stinging my eyes, nose , throat and hurting my lungs. I have been cleaning and ventilating for days even though its only 30 degrees outside. I've been searching with frustration of people who don't pay attention saying it's urine when I know it is not.

Thank you for an intelligent and more accurate answer. Now we can work on finding a solution that works. Any suggestions until the landlord gets here to fix it? How do I get it out of the warped wood floor?

Reply:

At ODORS GASES SMELLS, DIAGNOSIS & CURE - we give diagnostic suggestions for tracking down and fixing any odor including ammonia smells. Often indeed those are found to originate in urine but there could be other sources. First find the physical source

It would be unusual for ammonia smells to come from a leaky radiator but heating a radiator may cause it to emit odors from something that was painted on or spilled onto that device.

Question: leaks in heating boiler after shaking, rattling, and steam came out of floorboards

(Nov 17, 2014) joints in central heating leaking said:

Hi, we just put on the heating after summer. It seemed ok, but then the boiler started shaking and rattling and there was steam coming through the floorboards. It continued a bit after shutting off the boiler (gas, 24 y old).

Then, we found a leak in a metal T-joint leading off to radiators (near boiler). We have a mixture of metal and plastic piping. The joints are all metal of course. The leak was caused by the plastic pipe coming out of the joint. We replaced the joint. Refilled system with water.

Seemed OK, but this time a leak sprunt in the bathroom (2 floors up), again, plastic pipe into metal joint. We tightened a nut that seemed loose and it hasen't leaked since. We put on the heating with just that one bathroom radiator on to test it, but the boiler got very hot, the thermostat didnt seem to cut off. We switched everything off again.

We let it cool. The boiler man (on phone) said that just having one radiator on could have caused that problem, especially as the expansion tank is needing replacing (which will be done soon).

He said that if we switchen on more radiators everything should be ok.

We put on the heating, switched on extra radiators, everything seemed OK, but now two new leaks have just appeared: one in the pipe going into the radiator (rad was off at the time of leak) (again plastic pipe into a metal joint). The other leak is hidden behind boarding (that I am ripping down now) but it seems to on upright pipes on the 1st floor that bring heated water to radiators directly from boiler.

This is a 100 year old+ house, and we had some new rads installed 10 years ago on a tight budget.

I would appreciate if someone could explain a likely reason why the leaks are happening. Bad workmanship ? Too high pressure in system? Water too hot in system? The expansion tank ?

Thanks in advance for any comments at all.

I forgot to say that before the boiler got very hot and the thermostat didnt cut off, I had set it to 90 degrees celsius instead of the usual 60 degrees celsius.

which was a dumb thing, and we set it back afterwards.

me again, just to say that all the leaks are in separate places and on different joints. Basement = 1 leak, 1st floor= 1 leak, 2nd floor = 3 leaks (1 x hallway rad, 1 x near bathroom rad, 1 x big pipes that bring water to top of house (3rd floor)).

Reply:

Joints

Really? I can't imagine what a heating tech is thinking in saying it's ok to have steam coming up through a floor.

Leaks in stem piping are not fixed by turning on more radiators. It sounds as if you need help from a plumbing and heating contractor who is familiar with steam piping and controls.

Question: mold growth due to steam vent leaks

9 Jan 2015 Maria said:
I have a radiator that blows out vapor steam. So much that mold is growing on the wall and there are what looks like balls of jell on the ceiling as well. Is this harmful.

Reply:

Maria

One can't assess the harmfulness of mold by just a brief e-text but usually a large indoor mold reservoir that has grown on surfaces is at least allergenic and possibly pathogenic or toxic - depending on the genera/species and further depending on what the mold is growing-on. Large areas, more than 30 sqft. deserve professional cleaning.

You should repair or replace the steam vent that I infer from your note is failing to close when it should. Below I suggest that you continue reading at STEAM VENT REPAIR.

...


Continue reading at STEAM RADIATOR VENT REPAIR if your radiator leaks are at a steam radiator vent or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see BASEBOARD or RADIATOR LEAK REPAIR FAQs questions & answers posted originally in this article

Or see CHEMICAL TREATMENTS, BOILER for a discussion of leak-stop products used in heating systems

Suggested citation for this web page

LEAKS at BASEBOARD, CONVECTOR, RADIATOR at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

INDEX to RELATED ARTICLES: ARTICLE INDEX to ARTICLE INDEX to HEATING RADIATORS

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