Service Pressure

I have a 125 psi pressure-only relief valve on my water heater cold water inlet, about 2 feet before the tank (in addition to the normal 150 psi T&P valve). The pressure-only valve has been leaking for several months, between a pint to a gallon a day. I replaced the valve, same thing. I suspect my service pressure is too high and is causing it to open intermittently. Service pressure was 80 psi when I moved in 5 years ago (inspector commented it is at the upper limit). My questions: What is upper limit on service pressure from the utility? If it is high, should I expect them to install a regulator? Or does the homeowner get stuck with it. I'm calling the utility KCWD90 to check this, they replaced the meters at my place and the neighbors a few months ago, I seemed to notice this leak about then.
Thanks for any advice,
Rob

They replaced the meters at my place and the neighbors a few months ago, I seemed to notice this leak about then.

Click to expand...

I would guess that the new meters have check valves to prevent the water from the home from back siphoning into the water main.

You now have a "closed" system that requires an expansion tank.
When the water heats, it can no longer back up into the main.

http://www.amtrol.com/pdf/MC4090%2006_09%20TXT%20Brochure.pdf

When you cook, and heat water in a pan, the expanded air will lift the lid.
The expanded warm water is now lifting the relief valve and releasing pressure.
The expansion tanks prevents that by giving the added volume some space to work with.

http://www.amtrol.com/pdf/9015-087revDTXT.pdf

There is no limit on the pressure supplied to the house, but the upper limit on pressure IN the house is 80 PSI. It is up to you to install a regulator if the street pressure is higher.

Thanks Terry and Jimbo.
Terry, looks like I need an Amtrol ST8. Question: Does orientation of the expansion tank matter? The brochure shows them hanging below pipe. In my case, I don't have room, could I add a tee at end of the last rigid pipe before the corrugated line, and install it pointing up and angled out to clear the vent? I have a 50 gal tank in a corner, the rigid pipes are only a couple inches above the tank. (I tried but failed to attach a pic, "insert image" asked for a URL). Also, how is the air charge done (bicycle pump?) Any other changes needed to plumbing, could the diaphragm cause water hammer? And lastly, how urgent is this, any harm in letting the 125 psi valve continue to vent pressure awhile longer?
thanks again,
Rob

The expansion tank can point in any direction.
Some plumbers use a nipple at the tank, then a tee, a six inch nipple and then a 90 and thread the tank into that.
Brass, not galvanized.

Letting water through the 125 PSI valve isn't hurting anything.

It's a safety valve.
You're losing a bit of water, but so what.
Capping a safety valve would be dangerous.
http://www.waterheaterblast.com/

The tank doesn't help water hammer.
You may need hammer arrestors at the dishwasher, clothes washer and the ice maker.

valve

You have a 150 psi valve on the water heater, so why do you think you also need a 125 psi one in the system? Without an expansion tank, the 150 psi one by itself might possibly leak because even it would need the tank. The tank can be oriented in any position necessary, but it does need to be supported so it does not create stress and crack its mounting pipe.

In the Seattle/Renton area, if the water heater can't drain it's 150 PSI PRV, (It may be too far from a drain, or an outside wall) they will put in a 125 PSI on the cold in a higher location that can be drained.

That prevents the 150 PSI on the tank from getting carpet wet.

Not that many years ago, Bellevue used to require the 125 PSI on the cold.

Terry, that is an interesting concept. Around here in that situation we put a watts 210 temp. activated gas shutoff on the wh, and put a 125 or 150 psi relief on the cold pipe outside the building. Of course, we don't have freezing temps to contend with outside!

>>> Also, how is the air charge done (bicycle pump?) Any other changes needed to plumbing,<<<

Check your incomming pressure and set the expansion tank to that pressure before you install it. If you install a PRV you will have to change it to what you set your valve at, bicycle pump is fine.

Its an older 1968 house, WH inside ultility room. The 125 psi valve has a pipe run inside the wall to discharge outside the house. The T&P valve on the side of tank has a short pipe above a floor vent, so it (and any other leak) goes in the crawlspace.
Thanks again for the advice.