How to Diagnose Leaks in a Steam Boiler | Ask This Old House

Ask This Old House plumbing and heating expert Richard Trethewey helps locate the leak on a steam boiler that is losing water.

A homeowner's steam boiler is losing water, but there's no sign of a leak. Richard explains the problem and offers up a solution.

The homeowner was losing water because of a hole in the actual boiler sections that causes steam to leak into the exhaust pipe undetected. Ideally, Richard says steam boilers should never have to be refilled because the water should just continue to be re-circulated through the system.

Richard says the homeowner could keep the automatic water filler and the steam boiler would still work. However, that is wasting water, wasting oil to keep the boiler running and not very energy efficient.

Richard recommends installing a new heating system or a new steam boiler.

Later, in the workshop, Richard shows some other options for boiler replacement. One option is to install thermostatic radiator valves at each steam radiator. Another is to convert the steam radiators to hot water radiators by running an additional return pipe to each radiator.

To add air conditioning to the heating system, many people would remove the boiler and replace it with a forced air furnace and ductwork.

Steps for How to Diagnose Leaks in a Steam Boiler:
1. Set the thermostat at a high temperature to turn on the boiler, and leave it running during diagnosis.
2. Once the boiler has turned on, check the floor around the boiler. This would indicate a leak on the water side of the boiler.
3. Check all exposed piping, especially at the joints for a leak.
4. Check the main vent of the system to locate a leak.
5.If there are no leaks near the boiler, check the radiators in each room. Look for signs of water around the hand valve, at the connection of the steam pipe to the radiator, and at the air vent on each radiator.
6. If there are no obvious places where water is leaking, shut off the boiler and allow it to cool. When the boiler has cooled down, remove the vent pipe and inspect inside for any corrosion on the boiler itself.
7. Work with a qualified plumber or HVAC technician to repair any damaged or leaking areas.

About Ask This Old House TV:
Homeowners have a virtual truckload of questions for us on smaller projects, and we're ready to answer. Ask This Old House solves the steady stream of home improvement problems faced by our viewers—and we make house calls! Ask This Old House features some familiar faces from This Old House, including Kevin O'Connor, general contractor Tom Silva, plumbing and heating expert Richard Trethewey, and landscape contractor Roger Cook.

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How to Diagnose Leaks in a Steam Boiler | Ask This Old House

[cardo]

Richard is a plumber’s plumber. He Always provides helpful info.

[GeeEric]

I’m in NJ and have a steam boiler very similar to the one featured here. Been having problems with it and every “expert” I call has no experience with steam boilers. Need someone knowledgeable like this guy.

[jogog]

The HVAC guy who installed the automatic filler jerked the poor guy

[crapmusstank]

He said it's cleaned every year, how the hell did the tech not see that hole when brushing it out? Seems a little fishy to me...

[whidbeyhiker]

I've been working on boilers for 30+ years and have never worked on a single pipe steam boiler, have always had a condensate line, receiver, pump. Interesting to see this but man, I bet it can hammer. The HVAC guy who visited three times, failed to diagnose the leak and charged him to install a makeup water system that the system wasn't designed for apparently, like me, never worked on a single pipe steam boiler system either.

[richardhall]

The words no man ever wants to hear: "You're gonna have to get a new steam boiler."

[carcottrell]

I worked at Robinson supply for years. This guy Richard is a genius.

[joekatynski]

Don't agree with the 50 yr old water comment. You loose water due to evaporation in a steam system.
And a decent hvac tech should have found that during a maint

[Nneimp]

Follow up video please. That was interesting.

[ELEVOPR]

Wow, so it's a 5k-10k Problem. That makes me feel so much better now :o/

[lynnchello]

Another place is pin holes where the flame impinges on the bottom. The water leaks onto the burners and turns into steam.

[arabianknight]

Nice simple video. Not like other ppl where they talk your head off.

[petecheng]

When boiler starting to have a hole, you are done because you keep on putting fresh water into it means a lot of oxygen.

[BillyN]

I’ll say this as an hvac technician in Connecticut, the company that maintains that boiler should be fired. You pull the stack and brush it down. General inspection stuff.

[AT-ojof]

Hopefully he recommended a steam expert to do the new boiler, not a generalist heat specialist that does hot water or forced air. The near-boiler piping on that old boiler is bad, the main vent is tiny, and none of the mains are insulated. I had all those problems, and when the steam pros installed a new boiler they fixed those things and the system works like a dream. Dan Holohan talks about these things in his books and entertaining lectures.

[dx]

I Mean I watched a few other videos n this guy was dah best....

[appk]

OUCH! I’m going thru this right now, same exact problem.

[byraerthunberg]

Glad to see this I think I found the problem now have to check the warranty on the burnham oil burner.

[egold]

Simply run the boiler set at a higher temperature, go outside and check the chimney for white steam exhaust. Welcome a new boiler and Pope if you see this.

[mike-cqwk]

Why can't he just get a piece of metal and welded over it! Just an idea 🤔