View Single Post
  #5   Report Post  
Posted to alt.home.repair
Phisherman[_2_] Phisherman[_2_] is offline
external usenet poster
 
Posts: 1,597
Default Expansion water tank

On Tue, 18 Aug 2009 23:40:17 -0700 (PDT), fftt
wrote:

On Aug 18, 4:55*pm, Phisherman wrote:
I installed an expansion water tank when GE stated the warranty on the
water heater is void without one. * So, I charge the tank to 40psi as
stated and installed it fairly easily. *I'm on city water at about
70psi. *I noticed now that when the water is turned on anywhere in the
house, that a burst of water comes out the first couple seconds. *I
notice this most on the kitchen vegetable sprayer and both showers. *I
suppose this is supposed to happen, but it does not explain why.
Expansion tanks are supposed to help preserve water appliances.




The "why" is ......... an expansion tank is hydraulic bladder style
accumulator

There is a badder that keeps the water & air separated.

When you buy one it might be pre-charged to 40 to 50 psi. Or you
might have to pressurize to those levels.

When the unit installed & the water turned back on, the water at city
pressure (like 55 to 75psi) will flow into the accumulator driving the
air pressure up to the same as water pressure.'

Now you a pressurized system over air "over" water.


When you turn on a faucet, the water pressure in the system drops
slightly and the accumulator "squeezes" out some water to service the
demand. This will continue until the accumulator is empty.

cheers
Bob




That explains it, thanks. The tank is charged to 40psi, so when a
faucet is opened the expansion tank is preventing the pipe pressure
from falling below 40 psi. Before the expansion tank installation, a
faucet would temporarily lose some pressure. I guess this is a
benefit of the tank, but it's real purpose is to allow water to go
somewhere instead of an increase in pressure on the lines and inside
the water heater tank.