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Posted by Andrew on March 4, 2007, 2:51 pm
>
>
>
> >The pressure overflow valve on my furnace is leaking. It's a gas
> >fired hot water radiator system. I recently replaced the corroded
> >original, thinking that that was the problem, but it is persisting.
> >Here are the symptoms: The pressure gauge on the unit shows 30psi
> >which is the burst point for the pressure valve, hence the leak. If I
> >trigger the valve and fill up a bucket with water, I can get the
> >pressure gauge down to around zero, but within an hour it's back up to
> >30psi. I think the problem may be that the water supply valve to the
> >furnace has failed, allowing water to get by and raise the pressure.
> >Does that sound right? It feels like there's water flowing in the
> >supply line after I trigger the pressure relief valve, but the supply
> >has a ball valve, and I thought those things never failed...Could
> >there be some grit or corrosion in it? I want to make sure I
> >eliminate other possibilities before I cut the valve out and replace
> >it.
>
> >Thanks, Andrew
>
> Sounds very much as if your expansion tank is full of water. What to do about
it
> depends on the type of expansion tank you have. For mine, I shut a valve
leading
> to the tank, and then there is a valve on the tank that I open to drain out the
> water. I have a short length of garden hose that I attach to that valve so I
can
> direct the water into a bucket.
>
> CWM
Okay, I hadn't considered a failure in the expansion tank. Mine is
not isolated by a control valve, and there's no way to drain the water
from it without taking it off the system, and that would require
draining the whole thing. It DOES have a schraeder valve, however.
When I activated that valve with my fingernail, air came out and
lowered the pressure in the system (as registered on the pressure
gauge). And now the leak seems to have stopped and that lower
pressure has been maintained. Could this have been my problem all
along? Would excess air in the system find its way into the expansion
tank and stay there? I guess I'm not sure how that would happen. Any
idea what this symptom would suggest? The tank is clearly not full of
water, since some air at least came out, but is this a sign of failure
nevertheless?
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