Bubba wrote:

On Sun, 05 Mar 2006 00:27:32 GMT, Speedy Jim wrote:


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


Well, you seem to understand yet you dont seem to understand.
You might want to read this:
http://www.wattsreg.com/pdf/pg-prv.pdf
BUT
Lets just say you go to a customers home that has a newer water heater
and the relief valve seems to leak once or twice everyday or every
other day. You get there and the customer tells you:
She has had a plumber there 4 times to fix the leak over a month
period and its still leaking. The plumber has changed the relief valve
twice, and the PRV twice and then gave up. Yes, I got this call.
I looked at the water heater and relief valve. Nothing out of the
ordinary. I put my pressure gauge on the sink in the basement by the
water heater. It showed about 65 psi. Hmmm, nothing wrong yet.
Now I turn the water heater temp up and within less than 5 mins, my
pressure goes from 65psi to over 150 psi and starts leaking out the
relief valve.
The question is:
Do I replace the PRV and install an expansion tank?
Of course not. I installed and expansion tank and she was shocked that
was all it took. I later found out from the water utility that this
condo subdivision has water meters in a "pit" out in the front yard
with backflow preventers in them (as required by code).
Bubba


Yes, that's what I would have done too.
The expansion pressure buildup could have been
caused by _either_ the utility backflow preventer OR
the PRV.

From:
http://www.codecheck.com/pg15_16plumbing.html#waterpipe

Max. unregulated pressure 80psi . . . . . . . . . . . . . . .[2903.3.1]
{608.2}

Expansion tank req'd if regulator not internal bypass type [2903.4] {608.3}

------------
"Water heater manufacturers and plumbing codes require the installation
of an expansion control device if a backflow preventor, **pressure
reducing valve** or check valve is installed in the domestic supply line."

From:
http://www.amtrol.com/thermxtrol.htm

Jim