Gas Furnace Losing Water Mystery

craigycoup

Hi,
I recently had an issue with my furnace where the thermal safety switch went off. Had someone come by since I had no idea what happened and they corrected it. Ever since they left I've noticed that I am having to fill up my furnace with water half way through the day which wasn't the case before I had the issue with the safety switch. I have them coming back to take a look but looking for a second opinion. I have no obvious leaks of water or steam. I have tried shutting off the furnace, letting it go cold and then filling it up with water up to the top of the glass. Weird thing is that it loses water but only half way down the glass, then stops. This takes about an hour to happen once I fill it up. I find it weird if I suddenly have a leak after what had just happened with the safety switch but not ruling it out as anything's possible.

Thoughts?

Ironman

You may have a leaking wet return.

SuperTech

Could this also be a leak above the water line?

Jamie Hall

It's quite likely as the folks above have said that it's a leaking wet return. Further, it is quite likely that the leaking wet return caused the water level to drop when the boiler was firing (no water coming back) and that that was tripped the safety.

craigycoup

it was suggested to me that if it is a leaking wet return that, its usually easier to abandon the old line since the leak is most likely buried?

Ironman

craigycoup said:

it was suggested to me that if it is a leaking wet return that, its usually easier to abandon the old line since the leak is most likely buried?

That would depend on how the return is run. The line has to be below where it’s connected to the Hartford loop.

EBEBRATT-Ed

First thing if this is steam is to check the chimney for white smoke when it is running. It could be a wet return (that is the usual problem) it could be the boiler leaking above the water line. Hope not.

SuperTech

EBEBRATT-Ed said:

First thing if this is steam is to check the chimney for white smoke when it is running. It could be a wet return (that is the usual problem) it could be the boiler leaking above the water line. Hope not.

I'm glad I wasn't the only one to think a leak above the water line was a possibility. 

craigycoup

just to add some more. Heating folks came over yesterday and filled the furnace with water to the overflow and overnight, it lost no water...which I was surprised at. Before they left they were pretty convinced it was the wet return but given this, I'm not. The wet return is run along the floor of my basement with a section slightly raised right behind the furnace in which there is another valve. When I open this valve its def still filled with water. I'm assuming if there was a leak in my wet return that water wouldn't have drained out of this raised portion. In one sense in my original post it would point to a wet return leak but then in another sense it seems like I'm leaking steam somewhere. I'm reluctant to start cracking open my walls to replace the wet return given what I'm seeing.

Jamie Hall

What are you referring to as the "overflow"? The Hartford Loop? Consider. One purpose of the Hartford Loop is to prevent water from flowing from the boiler into the wet return. If that is your "overflow", then what you overnight test has shown you is that there is not a leak in the boiler below that level. It has given you noting about the wet return.

You mention opening a valve in a wet return and finding it filled with water -- but how high? Could there be water pooled in a low length of wet return, and yet a leak in the return at a higher elevation somewhere in the basement? There could.

Also, @EBEBRATT-Ed is right -- you could have a steam leak in the boiler above the water line. Unless the boiler was filled with water up to the header, this might not show up. Again -- what is that "overflow" to which you refer?

craigycoup

the overflow I'm referring to is at the top of the furnace to let out water. not sure what its called. Regarding the wet return valve, hard to describe without a drawing but basically the wet return runs along the floor of my basement but right behind the furnace there is a section that elbows up a couple of inches then runs about a couple of feet then elbows back down to the other side of the wet return so you could says it a higher point than the rest of the wet return. The valve is along this higher short run but all below the hartford loop. I'm assuming this wouldn't have water running out of it if it was higher point but a lot of my wet return is behind sheetrock so I can only see what starts to run behind the wall which runs along the floor.

neilc

can you post some pictures?

give us a general shot of the boiler, floor to ceiling, showing your overflow,
show us that wet return valve you got water from,

are all your wet returns above the basement floor?
any go into the floor and come up somewheres else,
or thru a foundation wall?
this would be your prime suspect,

the one behind the sheetrock,
what is your foundation wall? rubble stone?
and a water leak there is draining out, instead of in?

EBEBRATT-Ed

@craigycoup

If they really flooded the boiler and it did not leak overnight count your lucky stars that you do not need a new boiler.

You can lose more steam from packing leaks, air vents. etc If the boiler itself is ok I would fill the boiler up to the top of the sight glass and mark it with a sharpie or a plastic wire ty. Then let the boiler sit without running. If it's not the boiler and you loosing water it is the wet return. If you don't loose water you have some steam leaks

craigycoup

I left the furnace off the entire night so it was just sitting totally cold. I'll try what you suggest but any reason flooding it would not lose water overnight as opposed to just filling it to the top of the sight glass?

craigycoup

@neilc

here are some photos. tried to mark them up as best i could to show the raised portion of the wet return that has the valve.

are all your wet returns above the basement floor? - I believe so. Hard to tell since it goes behind the sheetrock and don't know past that. The basement was finished before i bought it but it was an old underground garage and from what I've seen so far, everything was exposed aside from sewage and water pipes coming in from the street.

what is your foundation wall? rubble stone? I'm in a brooklyn row house which i believe is all cinder block and brick.
and a water leak there is draining out, instead of in? possible but no way to tell without getting to behind the sheetrock. essentially if there is a leak, no idea where the water is going off to.

neilc

your pictures are a bit hard to see, blurry,

that first one marked wet return, sure looks like it is running up from under the floor slab,
am I wrong?
if any of your wet returns are under the floor they are suspect,

craigycoup

Yeah it’s hard to see but they aren’t running under, it just feeds to another pipe running along the floor.