Heating radiator leak troubleshooting:

This article describes how to find and fix leaks in hot water heating radiators. Where to Check for Leaks on Baseboards, Radiators, or Heating Convectors - How to identify, inspect, diagnose, and repair problems with hot water or steam radiators, baseboards, or heating convectors.

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.

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

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

Article Contents:

• LEAKS at BASEBOARD, CONVECTOR, RADIATOR
  • COMMON BASEBOARD LEAK LOCATIONS
  • COMMON STEAM RADIATOR LEAK LOCATIONS
  • CAST IRON RADIATOR LEAK REPAIR
  • STEEL RADIATOR LEAKS & REPAIRS

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.

On 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.

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).

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.

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.

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 Associates' 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:

• Steam is water vapor, and having been boiled, would not be itself a health concern but
  
  Watch out: steam vapor can cause burns.
• A leak of condensate out of your radiator (such as the leak shown at page top of this article) into the building structure risks rot, mold, damage
• It might be possible, when the radiator is cold, to repair the crack using a high temperature-resistant epoxy - you'll need to clean the surfaces first. Also,
  
  Watch out for lead paint on old radiators (see LEAD POISONING HAZARDS GUIDE)

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.

Using Epoxy to Repair a Leaky Cast Iron Radiator?

Question: how to repair a crack or leak in a cast iron radiator

2017/12/22 Justin said:

I just refitted a cast iron radiator that was on a steam system and added it to my water system.

It's the kind with the horizontal pipe across the top and bottom so it's definitely good for either application.

My problem is that it is unfortunately leaking. It's not leaking at any of the joints or anything but on one of the columns. There are no specific signs of cracks or damage, I haven't sanded the paint yet.

It's just sort of slowly seeping out. Is there any kind of repair I should attempt or should I just look around for another radiator?

This question and reply were posted originally

at BASEBOARD or RADIATOR LEAK REPAIR FAQs

Reply: possible use of repair expoxy on heating radiator leaks

If the radiator is cracked you might be able to make a temporary repair by cleaning paint down to bare metal and using a waterproof mending epoxy such as is used on automobile engine blocks (hence a hint at where to get it).

I would consider it only a temporary repair since I'd worried that the radiator may have or develop other leaks that cause a damaging flood when nobody is around to see the problem.

When you clean off the paint take care: if the radiator were for some reason badly rusted its iron may be thin and easily punctured.

Send me photos - or attach photos to your comment using the picture frame icon to the right of the Comment box - of what you find and I can comment further.

Ultimately you should expect to replace the radiator. When a leak has appeared in one spot I fear there are other imminent leaks just waiting to spring while you're out at the movies.

Reader follow-up: WaterWeld did not work

Here are some pictures of the radiator after removing the paint and my repair with JB Weld WaterWeld.

You can somewhat make out the hairline crack that runs a few inches down and around the column.

The WaterWeld did not work. I applied it while the radiator was shut off (both the send and return have a valve in the basement) and bled so there was only standing water pressure present.

I then closed the bleeder to make it even less likely for the leak to leak. It appeared to stay dry for the whole repair process.

I sanded and scuffed up and scored the surface too. I let it cure for over an hour.

A leak eventually formed through the putty (not around). The same thing happened when I tried a second application over it too.

Considering that JBWeld's WaterWeld is rated for 900psi/300°F it's pretty disappointing results.

I'm going to try regular ol JB Weld next, it's just applying that is more involved since its a bit runny and it's a vertical surface.

If the JB Weld doesn't work as is I may attempt to fully address the crack by drilling and beveling it, but since the radiator is still in service I really don't want to get that involved with disconnecting and draining it.

Reply:

That epoxy repair product has worked for me on both automobile crankcases and on heating radiators, but mixing the two components well is quite important.

Reader follow-up:

I will say that the epoxy putty repair has gone back and forth leaking and not leaking.

It formed a few different pin hole leaks that seem to have stopped leaking. Similarly the whole repair pulled away from the radiator and leaked and then stopped leaking. I'm wondering if the heating/cooling cycles are causing this.

Either way it seems to be fine to last the season and I'll attempt the real repair with regular JB Weld in the spring.- Anonymous 2018/01/02

Spotting & Fixing Leaks in Steel Heating Radiators

The steel radiator 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 radiator 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.

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

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

These Q&A's have moved to BASEBOARD or RADIATOR LEAK REPAIR FAQs

...

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

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

Or see these

Recommended Articles

• CHEMICAL TREATMENTS, BOILER for a discussion of leak-stop products used in heating systems
• WALL CONVECTOR HEATING UNITS

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INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING RADIATORS

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