Bill Smith wrote:
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
water.

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.

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...

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?

Bill

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.

HTH,

Jeff
--
My name is Jeff Wisnia and I approved this message....

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"