Water keeps filling

mrbill08809

The psi pressure gauge goes down to zero every couple of hours. I fill it to 20 psi with the fast fill but it goes down again. The automatic fill stoped working so I fill it manually. I see no leaks on the furnace.  Any suggestions 

EdTheHeaterMan

Is it a closed system? If yes there is a leak. You need to find it.

hot_rod

What type of heat emitters? Any underground piping?

rick in Alaska

Have you tried filling it and then leaving the burner shut off for a while? If so, does it stay at pressure, or does it still fall off? There is a possibility it is leaking inside the burner box, and gets burned off as the burner is running, so you wouldn't see it leaking when it is running.
I had a 500,000 btu boiler that only leaked when the burner was running. As soon as the burner came on, it would start pouring water out a crack in the casting on the outside of the firebox.
Rick

mrbill08809

hot_rod said:

What type of heat emitters? Any underground piping?

Baseboard heating

HomerJSmith

Not to get technical, it's a boiler not a furnace.

Look for leaks, shut off zones, one at a time, if you can, and see what happens. Does your boiler pressure relief valve empty outside or some where you might not see a discharge?

What does the tridicator (pressure-temperature gauge) on the boiler say after you fill it and fire it up? Does the decrease in pressure occur even if the boiler isn't firing?

Perhaps you have piping under the house in a crawl space servicing your baseboard and the leak is there. I guess you don't have baseboard on a concrete slab being serviced by piping in the slab.

Leaks in a slab can often be spotted with a thermal camera.

It only takes a couple cups of water loss to drop a boiler pressure gauge to 0.

Charlie from wmass

What type of boiler? Photo of boiler please

Paul Formisano

Assuming this is a cast iron steam boiler, you probably have a crack in the casting.  When it heats up, the crack opens more due to thermal expansion and lets water out.  Meanwhile the water gets turned to steam and water vapor and goes up the chimney so you never see the leak.  Remove the burner access door when it’s running and look and listen very carefully.  If this is happening you’ll hear the water hissing as it drips out and hits the burner.  If this is the problem you’ll need a new boiler as it is probably too rusted out to be worth fixing.

Charlie from wmass

Paul Formisano said:

Assuming this is a cast iron steam boiler, you probably have a crack in the casting.  When it heats up, the crack opens more due to thermal expansion and lets water out.  Meanwhile the water gets turned to steam and water vapor and goes up the chimney so you never see the leak.  Remove the burner access door when it’s running and look and listen very carefully.  If this is happening you’ll hear the water hissing as it drips out and hits the burner.  If this is the problem you’ll need a new boiler as it is probably too rusted out to be worth fixing.

I certainly hope he does not have a steam boiler hooked up to baseboard and he is filling it to 20 psi.

JAdams

mrbill08809 said:

The psi pressure gauge goes down to zero every couple of hours. I fill it to 20 psi with the fast fill but it goes down again. The automatic fill stoped working so I fill it manually. I see no leaks on the furnace.  Any suggestions 

How long has this been going on? Have you checked the expansion tank? If a diaphragm tank did you check the pressure? Can you isolate the zones from the boiler and pressure test them and the boiler individually?

Trying to find a small leak can be time-consuming and frustrating. You have to start by eliminating the components (expansion tank)and go from there. If you're not a heating professional, I suggest you hire one to find out what's going on.

Mark Eatherton

Simple means of finding it. Replace the pressure reducing valve so it works. Electrically disconnect the circulator(s). Turn thermostat up so boiler heats up to limit (typically 180 degrees F). Let it set for a while. Now start (CAREFULLY) feeling the pipes connected to the boiler (supply AND return) and follow the hot pipe. Pressure flows from high to low. The water will be flowing towards the leak. With baseboard, it is common to have a leak in the jumpers that go under ground between the ends of the baseboard. This method will ONLY work if the boiler is cast iron. If it is something else, don't do it. You will melt the heat exchanger down. If you can gain access to an infrared camera (local fire department?) then you can "see" the heat in color. Prepare to do jack hammer surgery...

johnre9999

I didn't see anyone question the relief valves specifically so figured I would chime in. Is the relief hard piped directly to a drain? If so, it may be reliving without your knowledge. It also may have been exercised and is now weak. Even if you have addressed an expansion tank issue in the past, the relief can still be the source due to it now being out of calibration or debris stuck in the seat. As suggested by JAdams check your expansion tank as part of this diagnosis pathway as that is often the initial cause of a weeping relief valve. This could also be the case if you have a backflow prevention device. A seat could have failed and if it is hard piped it too could be discharging to a drain without your knowledge.

MarkMurf

How about draining the system and air pressure testing the whole thing ? Then creep around the house on yer hands and knees listening for sssssister sssssssuzie in her sssssshort sssssskirt ?

pell

What happened to Mr. Bill. Are there pipes in concrete? My guess is internal leak, when the burner fires. This is what I refer to as "smoke on the water".

JAdams

So what have you figured out Mr. Bill, anything? I'm kinda curious to find out. I'm sure some of the other guys are curious as well.

jeffydiver

In Steam systems, the Condensate Drain Line is clogged. If it's not serviced, it'll start coming out of the First Floor radiators. I take a reciprocating saw and removed the drain piping and install new replacement piping. Sometimes you can be lucky and force the drain clean with a hose, but don't bet on it.

Lance

Divide and conquer. One must isolate the boiler from the system. Test both sides for a pressure drop. Than you can make the next informed step. If a hydronic vessel is leaking while running and no water is ever found, a view of the chimney top may see a white cloud of vapor indicating an internal leak to the flue. Otherwise to confirm a pressure drop test is a must to pin point the source no until the isolated part or section is found.
Furnace is a device used for heating. The name derives from the Greek word fornax. What it heats, air, water, or iron ore, for some who care, we can further define it. In our town, boiler and furnace are used alike.