DIYbanter - View Single Post - How do I know if my expansion tank is water logged?

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wrote:
The story begins when I dicovered that the relief valve (of my home's
heating system gas-based heater) discharges about 1/4 cup of water
daily.

A technician from the gas company (called for a different problem) that
saw this immediately pointed to the Amtrol expansion tank (Extrol model
#30) as the culprit. He said he could tell just by knocking on the tank
and listening whether it is a hollow sound or not.

After he went, I tried this myself but I actually noticed that the top
part (which should be filled with water) does not sound hollow, while
the bottom part (which should be filled with air only) sounds hollow.
Isn't this the way it is supposed to be? If so, what made him say this
is the expansion tank?

Also, while he said that the expansion tank should be replaced, I
noticed a threaded air valve at the bottom of the tank, which looks
like exactly the ones found in bicycle tubes. Is it possible that I can
get away with simply re-filling some air in the tank, instead of going
into the expense of replacing the tank?

It should be noted that I have no intention of replacing the tank
myself, but rather let a professional heating plubmer do that. However,
I feel that I need to gather as much information about the problem as
possible, before going ahead with ordering a repair. One plumber I
called said the expansion tank alone will cost me $250 (excluding
labor!). I found that same exact tank for sale on the Internet $43.55
...

Thanks!
Sam

put an auto tire pressure guage on the air valve and check the pressure
is still as specified in the owners manual.

If water comes out of the air valve you need a new tank , or a repair
kit.