After changing a leaky pressure relief valve on my furnace, I noticed that
the diaphragm expantion tank in my hot water heating system was filled with
I shut off the supply and opened the pressure relief valve. I then pushed on
the pin in the bicycle-tire valve on the expansion tank and let all the
water drain out of it through the boiler and out the expansion tank.
So far so good.
I am not sure if the diaphragm failed or I need to recharge the expansion
tank with air.
Can anyone tell me the procedure for recharging it?
That last sentence is a little confusing. It reads like you let the
water drain out of that little "tire valve", but I'm assuming that's not
what you really meant to say...
You probably should have pushed in on the pin of that "tire valve"
BEFORE you shut things off and drained the tank. If water came out of it
you'd have known the diaphragm was "holy".
But, you can try pump air in through that valve now with a bike pump,
checking the pressure with a tire gage as you go. If you can't build up
any pressure at all, then the diaphragm is shot. If you can build up say
20 psi or so and it "holds" for an hour, then the diaphragm's ok.
Assuming it IS ok, just pump more air in until you reach a pressure
about equal to the pressure you normally see on your heating system's
gage and then refill the heating system.
That's the way I do it.
My name is Jeff Wisnia and I approved this message....
Thanx for the replies.
When I try to pump it up, I head gurgling sounds when I shut off the air
pump. So I suspect you are all right that the diaphragm is shot so I'll
replace the tank.
I'm pretty sure the PRV was shot anyhow. It was not just discharging under
pressure, it was dripping quite a bit too.
There should be no water in the lower (air) chamber. It's shot. And
since it's no longer absorbing the thermal expansion, that's why your
relief valve tripped. Buy a new tank (mine was $40 at Menards a few
years ago). It came pre-pressurized to 40 psi. You may have to
replace the relief valve as well -- in my limited experience, an old
valve does not reseal well after tripping.
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