montana wrote:

I've been Googling former posts to the group on tis question, but
evidently i can't wrap my tiny brane around what I've read. DH has a
double and there are two water heaters tied to one expansion tank. The
HVAC guy hooked up the expension tank because there had been problems
with the relief valves leaking before and this was supposed to fix it.
It didn't. I suggested that DH may need to get a pressure regulator at
the point that the water comes into the double from the city.

He doesn't want to do this or have it done now, but I know he's had
these relief valves changed out before. His arthritis is acting up, so
he was pretty snippy when he asked me if I could do the work myself and
just do another quick fix until the day comes that he gets the other
pressure regulator put in. I love the HVAC guy, but he charges an arm &
a leg & I don't think he always does the best job.

So; can an amateur replace these valves without too much trouble? SNIP

Find out what the pipe size is from the meter into the house;
that will dictate what size reducing valve (PRV) to get.
As RikC suggested, making a pressure measurement needs to be
done first. You can buy an inexpensive gauge to mate with
a hose bibb.

If street presure is below, say 80 PSI, there may be a check
valve or backflow preventer which is making the expansion tank
necessary.

One expansion tank may not be enough for TWO water heaters;
the tanks are sized by gallonage because that controls the
amount of expansion. I would rather have 2 separate expansion tanks.

Couple of links:
http://www.flexconind.com/html/wh-series_.html

http://www.wattsreg.com/


Jim