Bubba wrote:

On Sat, 04 Mar 2006 23:30:33 GMT, Speedy Jim wrote:
SNIP

Jim,
You are just a bit off. You dont install a press red valve AND an
expansion tank if the incoming pressure is over 80psi.\]
Those 2 parts correct 2 completely different issues.
The pressure reducing valve is almost self explainatory. It is used to
reduce the incoming city water pressure to a more manageable pressure.
The expansion tank is used when a back flow preventer is installed
somewhere in the city water system.

Sorry, have to beg to disagree.

I fully understand the purpose of the PRV.
However, the PRV creates a closed system, just the way a backflow
device does. Yes, *some* PRV's incorporate a bypass check valve
to bleed off pressure from expansion, but they quickly clog up
or else the street pressure is too high to allow bypass.

Good practice and, frequently, inspector requirement is to
install an exp tank anytime a PRV is used.

Jim