"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