Expansion water tank

[Phisherman]

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.

[Joe]

If your city water pressure is 70 PSI it should be regulated down to something closer to the expansion tank setting. High water pressures have always been cited as rough on home plumbing systems. When you have the two in balance the water bursts will disappear. The lower pressure should add years to the life of the water heater.

Joe

[George]

An expansion tank isn't a regulator and is only part of what you need for a proper design when you have high water pressure. Installing a regulator will produce a good result.

[The Daring Dufas]

All of the standard potable water pressure regulators I've ever installed, were factory set to 50lb pressure. You can have pressure spikes coming from the municipal supply that can damage toilet tank valves, blow faucet washers and cause the T/P valve on the water heater to leak. You might consider a pressure regulator on your water supply.

TDD

[fftt]

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

[Phisherman]

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.

[fftt]

yes, since ...worst case oyu could have a whole water heater of cold water (all the hot got used up)

the water is heated and expands by xx%

if NO hot water is used during the heating process....than depending on the "cold" to "hot" temperature delta, on a 40 gal W/H you get about 1 galllon of expansison.

I think that a lot installs use a tank that is too small & probably are under pressurized as well. I discussed my install with my plumber & I opted for an adjustable relief valve set to ~80psi instead of an expansion tank. The system dumps a less then a few quarts per day into a flower bed

here;s a link to a sizing discussion

[trader4]

Sounds like a poor solution to me. Here in NJ, expansion tanks are generally not used on systems with municipal water and they pass inspection and cause no problems. If the pressure in the system is spiking to over 80PSI, I'd put in a pressure regulator to fix the problem the right way, which would allow the pressure to be set at a more normal 50-60 PSI for the house.

[George]

I agree on the poor solution part.

Are you sure the People's Republic doesn't require backflow prevention on municipal water? That has been a requirement in PA on new installs for a long time.

[The Daring Dufas]

I'm wondering, with the use of PEX plumbing becoming more prevalent, if the plumbing system in the whole house may act like a long stringy expansion tank? This could make expansion tanks unnecessary.

TDD

[fftt]

[fftt]

George-

I discussed these options with my licensed professional (commercial) plumber.....please explain why this a "poor solution"

Its been working fine for 2.5 years & no problems.

cheers Bob