Reasons why the system is losing water (that doesn't return), and where to look for solutions

HeatingHelp

Reasons why the system is losing water (that doesn't return), and where to look for solutions

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Controlsgirl

Thanks so much for the practical advice! It has been pretty hard for me to find.

EBEBRATT-Ed

Yeah, when cold weather hit's (like now) we get a lot of these "service calls" on the Wall

Phil_17

You left out the radiator valves... My system started losing water and it turned out to be a couple of valves that need to have the packing redone. A really simple thing to do, but it took me months to figure it out.

Labenaqui

Double-doped all iron near-boiler piping ..... "old school" works.

rjfork

Excellent article. Experienced nearly all of those issues. First a leaky return pipe, which didn’t solve the constantly evaporating water from the boiler. Turned out the boiler had a hole as described above. A new boiler along with replacing the radiator values has the system finally working properly and retaining the proper water levels.

Jason_13

Don’t forget chloride issues. As Dan stated oxygen will create holes at the disengaging area, water line, but chloride erosion is at the top of the castings.

Erik_condo_treasurer

I would love to see a post like this for hot-water systems. Our five-story condo, a brownstone row house in Brooklyn, got a new boiler about 15 years ago. Apparently the tank in the ceiling above it was not connected to the boiler (they are physically connected, but maybe valves were closed to cut it off). I think that tank is designed to replace water that escapes from the system.

In any event, for a while our boiler was releasing water through the relief valve onto the floor of the boiler room to alleviate high pressure (40+ PSI). Adjusting the pressure down (I think with the reducing valve) solved that problem, but then the boiler did not consistently push hot water up to the top-floor radiators. PSI needs to be 25 to reach the fifth floor, but occasionally it drops to 24, and the top floor would get cold.

When that happened, we would briefly open a valve by the reducing valve to feed more water into the system. But this became a weekly chore. We needed a permanent solution. We hired a plumber familiar with old Brooklyn buildings and he put in a small expansion tank on the floor next to the boiler. The reservoir appeared to help, but not as much as the plumber thought. Instead of adding water every week, the top-floor unit owner is adding water every month. Our plumber says adding a second expansion tank could fix this. What do you think? And how might water be disappearing from our system? Should we reconnect the big expansion tank in the ceiling above the boiler?

Jamie Hall

Good grief. Yes, that big expansion tank in the ceiling above the boiler is the key to the whole thing.

It's actually called a compression tank — and it performs the same function as the modern expansion tanks, only simpler. Draining it and reconnecting it properly will probably do the job.

However.

If your plumber isn't familiar with it, though, it's unlikely that he can do it right — and his solution of adding another expansion tank to your system will work — it it's big enough. You're going to need an EX-90 as a guess, but your plumber should confirm that.

bburd

All hot water space heating systems need provision for expansion of the water as it is heated. The size of the expansion (or compression) tank depends on the volume of water in the system. This means a system with traditional cast-iron radiators will need a much larger tank than a system with fin tube or modern panel radiators. Your plumber may not be familiar with the methods for calculating the water volume and sizing the tank.

Have you tried the "find a contractor" feature of this site?