"Don Young" wrote in message
...

"HarryS" wrote in message
news:i9Mch.168881$aJ.146294@attbi_s21...

"Joe" wrote in message
.. .
3 days ago I noticed water leaking out of the pop off valve on my three
year old hot water heater. My first thought was bad pop off valve so I
replaced it. The problem persisted. Then I thought maybe the thermostat
was sticking on and over heating the water so I bought a thermometer and
check the water temp at the closest faucet to the tank and the water was
130 deg with the tank set on 125. I then thought I must be having water
pressure spikes so I bought a pressure tester and screwed it into the pop
off valve outlet and just left the pop off valve open. Initially there
was only 75 pounds of pressure. I went back and checked an hour later and
the gauge showed the pressure had been as high as 160 pounds. I thought
ok my water pressure regulator had bad so I replaced the regulator coming
into the house and the pressure was 60 pounds initially. I come back and
hour later and the pressure gage had gone up to 200 pounds which tells me
if the gauge had not been there the pop off valve would have again let
water escape as it is designed to pop at 150 PSI or 210 degrees. The hot
water in my house is not scalding hot by a long shot.

Where do I go from here? Why is so much pressure building up in my water
heater?

Thanks Joe


I had the same thing happen. Everything worked fine for years until one
day water started to leak intermittently from the relief valve. I put on
a new relief valve but that didn't stop it. I lowered the house pressure
at the regulator; still no change. So, I installed a pressure tank and
the problem went away.

I asked myself the same question you're asking. Why, after all these
years, did this problem crop up? I could only come up with two
possibilities. 1. My pressure regulator had a bypass valve (orifice)
that had plugged. 2. The water company had installed a backflow
preventor at the meter (or perhaps changed the meter to a type that has a
backflow preventor built in).

I didn't pursue the real reason, but I'm betting it was No. 1.

Harry


A third possibility is that the mains water pressure has been increased to
above the valves relief setting. This would prevent the bypass orfice from
being effective. If the main is 150PSI and it is regulated down to 60PSI,
the bypass will work only when the house pressure goes above 150.

In any case, a working expansion tank will solve the problem. A
waterlogged expansion tank is no longer effective and needs to be drained
and/or re-pressurized.

Don Young


You're correct. In my case, I knew the pressure coming to the house wasn't
the culprit. My outside hydrants get mains pressure and, while higher than
the regulated pressure, it's considerably lower than the pop-off pressure of
the relief valve. It's nice for me to have maximum pressure outside,
however, I wouldn't want 150 psi on my hoses.

Another thing to consider is that many homes have anti-hammer devices
installed throughout the house. These can offer some of the same protection
as a pressure tank. However, if they are the type that can waterlog, you
can lose their protective effect over time. The best way to check this out
is to completely drain down the system, refill, then watch to see what
happens to the relief valve.

It's also a good idea to have a pressure gauge installed so that you can
actually see what is happening with the water pressure in the home.

Harry