Joe wrote:

I have a regulator coming into the house which I replaced today.

Why would I need an expansion tank now when there has not been one for the
last 9 years I have owned this house and it has not been a problem up till
now? What has changed?
Joe


Some PRV's have a "bypass" check which will allow a trickle of water
to go back to the street *if* street pressure is low enough.
But over the years, the bypass port gets clogged and no longer works.
Then the pressure skyrockets.
This is the reason that Codes require a thermal expansion tank
in the presence of a PRV, whether or not it has a bypass.

So, get thee to yon BigBox and buy an expansion tank.

Jim



wrote in message
ups.com...

do you have a anti siphon valve at the water line entrance? if so you
need a pressure tank.

with no abilty to backflow when your heater heats water it expands and
causes the valve to open.

if not you need a pressure regulator valve installed at the entrance