How to fix leak in steam boiler?

Dan Gabig

I have a Burnham iron boiler dating from 1989 for my single family residential steam radiator system which has developed a leak. The steam condensate drips down onto the burner tubes and of course, steams off into the exhaust vent, turning the exhaust into a steam condensate cloud on cold evenings and mornings. The copper header pipes do not appear to be leaking as they are clean of any residues on The condensate and rusty junk form on the outside of the boiler. I recently had a lot of burned on condensate and rusty crude scrapped off the outside of the boiler as the burners were not able to vent properly as the passages between the cast iron boiler tubes were clogged almost shut. Now a persistent leak occurs only when the fire is burning and steam is being generated. It does not leak when the boiler is not being fired, which would seem to indicate that the leak is above the water line or the leak only opens below the water line when under the influence of the heat of the direct fire. I suspect the leak is steam exiting a crack or hole above the water line. I really don't want to have to take the exhaust cover off the boiler again to find it and I'm not so sure I would spot it unless the steam was escaping the hole or crack which may require the unit to be fired which one simply can't do with the top off. I will try to fill the boiler up to the headers by manually by-passing the fill water solenoid switch and see if water leaks from the boiler when it is not being fired, perhaps then I could spot the leak by taking the top off again. But I would have to reseal the top with furnace cement and would prefer to perhaps give a go with the stop leak product(s) to cure the problem with out disassembling the boiler once again.

I wish to learn the options as to how to fix a leak. I have been told by the HVAC repair personnel that there are a number of "stop-leak" products that are effective in sealing small leaks and cracks in low pressure cast iron boilers. One such manufacturer is Hercules Chemical Company which makes Boiler Solder a free flowing powder that is mixed with water and put into the boiler after removing the pressure relief valve and another product by Hercules is Boiler Liquid which seems to be the same powder that is premixed into a liquid concentrate for insertion into steam or hot water boilers via the pressure relief valve opening. Hercules, the manufacturer, says that products will not clog the system or cause offensive odors and will not interfere with normal boiler operations.

Have you any experience with such "stop leak" products with low pressure steam boilers and if so, how effective have they been in stopping the problem? Also, any downsides to utilizing them?

Hercules also suggests using their Pro Poxy 20 (a two part gray expoxy) to fix larger holes of cracks in areas not exposed to the flames from the burners. They say this epoxy is good up to 300 degrees farenheit for extended periods of time. I suspect that if the epoxy is used near a flame that it would simply burn off after all it is polymer based. I'm not sure how far from the flames such an epoxy "plug" would need to be to avoid harmful direct heat, but it would seem almost anywhere inside the fire box would be a very high temperature, perhaps higher than 300 degree farenheit, after all the metal of the boiler has to get hot enough generate steam.

For larger cracks or holes not suitable for "stop leak" products what is the preferred method of fixing such leaks?

Thanks for the input. Looking forward to not having my burner tubes getting dripped on a messed up and of course, having the system call for make up water.

Best regards,

Dan

Josh M.

Realistically those products might not work in your situation. Burnam cast iron sectional boilers use a push nipple to seal between the sections. Most leaks occur between the sections. Other leaks come from thermal shock where cold water enters the boiler and causes the metal to contract quickly. Usually however thermal shock tends to produce gushers. If the leak is between your sections contact your local burnam dealer and order the specific nipples for you boiler. They can usually supply you with directions for proper installation. However since the boiler only "leaks" when fired I almost wonder if the boiler might be condensing. This is rare with steam boilers but you can test it by placing a spoon in your flue pipe and seeing if it fogs up.

Tombig_2

Dan...

It's a waste of time and money to try any stop leak additive for a leak above the water line. If you want, strip the sheet metal, fill to the header and SEE the leak. Any epoxy or other patch will be temporary at best. Replace the section or replace the boiler.

Steamhead

I hate to have to tell you this

but that boiler has had it. Instead of wasting your time trying to patch it, go to the Find a Professional page of this site to find someone who can replace it properly. One such qualification is NOT using copper pipe on the steam header.

A good steam man can also find anything out in the system that may have helped cause the boiler to leak. These include, but are not limited to: inadequate venting, improperly piped feed water line, no Hartford Loop, clogged returns, etc etc. This will help keep the new boiler from meeting an early demise.

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steve_38

steam leak

it sounds like the leak is coming from the crown sheet of
the boiler. if it is that, you'll have to replace the boiler. have a professional look at it. most likely you'll need a new boiler. also note: if the the leak is coming from a push nipple. it's crazy to try and atempt to fix that. you would have to disconnect the piping and split the sections of the boiler. not worth the time and effort. and i believe there is only a year warranty on steam boilers, because steam is very corrosive and tippically problems like that occur on steam systems... i've been on many steam leak calls and the comes in as " customer has to constantly add water to system more then normal "... perfect example -
I get a call in hempstead for a steam leak, 2 problems i found not only steam pressure problem but the boiler had a lot of back pressure. I opened up the top lid of the boiler, not only was it plugged but i found a pin hole at the crown sheet of the boiler, bingo! easy find! i told the customer that he needed a new boiler. he asked me if I could weld, and i told him no, i would not recomend trying to seal it up. he was a C.O.D. customer and he still did not get a new boiler and has found knowone to seal it up...
it must be a money issue with him. some leaks can be a little hard to find, but an expert should be able to find them.

Tombig_2

Steam is Corrosive?

> it sounds like the leak is coming from the crown

> sheet of the boiler. if it is that, you'll have

> to replace the boiler. have a professional look

> at it. most likely you'll need a new boiler. also

> note: if the the leak is coming from a push

> nipple. it's crazy to try and atempt to fix that.

> you would have to disconnect the piping and split

> the sections of the boiler. not worth the time

> and effort. and i believe there is only a year

> warranty on steam boilers, because steam is very

> corrosive and tippically problems like that occur

> on steam systems... i've been on many steam leak

> calls and the comes in as " customer has to

> constantly add water to system more then normal

> "... perfect example - I get a call in

> hempstead for a steam leak, 2 problems i found

> not only steam pressure problem but the boiler

> had a lot of back pressure. I opened up the top

> lid of the boiler, not only was it plugged but i

> found a pin hole at the crown sheet of the

> boiler, bingo! easy find! i told the customer

> that he needed a new boiler. he asked me if I

> could weld, and i told him no, i would not

> recomend trying to seal it up. he was a C.O.D.

> customer and he still did not get a new boiler

> and has found knowone to seal it up... it must

> be a money issue with him. some leaks can be a

> little hard to find, but an expert should be able

> to find them.

Tombig_2

Steam is Corrosive?



Wow! That's a tough one to swallow.

steve_38

OK

What's so tuff about it?

Mark Hunt

Actually


steam itself is not the issue.

Disolved oxygen in the liquid water is removed when you heat the water. When the water cools, it re-absorbs gases. Carbon Dioxide is re-absorbed easier than oxygen so the Ph of the liquid water drops.

Hope this helps.

Mark H

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Tombig_2

In short...


Steam is vaporized water. It's not corrosive. Most corrosion causing elments are in the boiler and piping below the water line. Ever taken apart a 100yr old steam line? Ever even SEEN a 100yr old domestic water line? I rest my case.

steve_38

ok but

i didn't say the pipping is corrosive, i said steam heating is corrosive, which it is if it's not maintained. i work in NY which is loaded with steam systems.

Ken_8

Steam does not cause rust.

Oxygen does.

When the heat's off, the steam collapses and returns to the boiler leaving everything above the water line to be in the presence of what's left to fill the system. That "stuff" is air.

Air is 19% oxygen. The oxygen in the air works on the insides of the system (radiators, supply piping, return piping, near boiler piping, and the inside of the boiler above the water line) and even the inside of the boiler below the water line via absorption of air to a very small degree, in the boiler water itself.

This is normal.

This has been known for over 200 years and is easily delayed by water cleanliness, raising the pH, and a bunch of very small but important things we can do, as well as the homeowner, to minimize the impact.

We find using copper pipe in anywhere in the system seems to accelerate corrosion. It has physical dynamics which are also undesireable. But then, so does running a typical steam system at over 2 p.s.i., failing to blow down, bad vents, etc.

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steve_38

And Again

I never said steam causes rust...
i'm just saying steam systems overall compare to
hydrodic systems is more corrosive (fact) i work on them
for a living. thats why steam systems need more attention then hydronic systems.

Tombig_2

Steve

Sorry, I was just being cynical yesterday I guess. Above the water line the pipes do stay in pretty good shape though. Dan's boiler, at only 15 yrs, was probably ill maintained, combustion related or some other issue.

gerry gill

i'm curious,

we dont use copper anywhere on a steam system, at our company cause one of the local old timers who is really into physics with his plumbing taught us that copper in contact with steel and connected with water becomes a battery..anyone else ever hear of this..we were taught that this is what accelerates the corrossion so we dont use copper..

tombig

Dielectric

unions are a necessity in the domestic water world. Under the right conditions, copper and steel WILL make a battery and cause excessive oxidation. Closed systems tolerate Cu-Fe connections much better. Steam should never see copper unless it's below the water line.

Unknown

Gerry

We advise against using copper on steam piping with our boilers for several reasons. The possibility of an electrolitic action is one, expansion and contraction along with the presence of large amounts of solder flux are others. Once the flux gets into the pores of the iron, it's a bear to get back out. It sounds as though this gentleman has encountered an internal corrosion issue. The reasons for this are many, the majority of which are caused by excessive amounts of make-up water via a water feeder and acidity caused by poor venting and CO2 coming back to the boiler as acid. It is not advisable to change a section as the others have probably encountered the same problem. Hope this helps.

Glenn Stanton

Burnham Hydronics

reb617

Steam leaks.

@TOMBIG, Steam is very corrosive,Mark Hunt is correct.I am a state licensed steam engineer and pending on city water, the water is acidic and we add neutralizing amines to the steam to neutralize condensate.We also add caustic to the city water to create a balance to the water.

reb617

Steam leaks.

@TOMBIG, Steam is very corrosive,Mark Hunt is correct.I am a state licensed steam engineer and pending on city water, the water is acidic and we add neutralizing amines to the steam to neutralize condensate.We also add caustic to the city water to create a balance to the water.

nicholas bonham-carter

Cause of section failure

I have a theory about these sort of upper waterline cracks:

If the main venting is grossly inadequate, and the boiler stops firing, in the intense vacuum which develops in the piping, the waterline can plunge as water is sucked up into the wet returns. When this happens, the thermal stress to the cast iron is severe, and could cause unequal expansion/contraction-an opening for corrosion to start. As also noted, the presence of unvented CO2 when mixed with water is acid enough to start the corrosive process.--NBC

rmoore007ri

dielectric unions and steam boilers

What l've learned about steam heat comes largely from Dan Holohan's writings.

The near boiler piping seems to often be re-done with copper with no dielectric union between that and the old iron piping. This forms a galvanic union and there is a voltage gradient along it's length. The rule is that iron loses to copper. so the first pinhole leak will likely be in some 2nd floor closet piping. But this will take years. So hey, what could that boiler installation fifteen years ago have to do with the leak on the 2nd floor eh ??

The other location where there needs to be a dielectric union is the copper waterline feed to the boiler.

bob moore