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robbz
Member
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Posted: Sat Aug 9th, 2008 05:19 pm |
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hi plumbers, great site.
would lowering the temperature of an electric hwt reduce thremo expansion?
thanks
robbz
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eleent
Member
| Joined: | Sat Sep 11th, 2004 |
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| Posts: | 1565 |
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Posted: Sat Aug 9th, 2008 11:09 pm |
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Hello: The easy answer is yes. If you heat the water 20 degrees instead of 40, you'll get essentially half of the expansion.
Yours, Larry
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robbz
Member
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Posted: Sun Aug 10th, 2008 06:49 pm |
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thanks.
I suspect a thermo expansion problem. As mentioned in forums, I have checked the water pressure: I got 80 psi (prv set ok) checked at silcock. water drops to 50 psi when using water at sinks or flushing. HWT measures 90 psi from tank drain, drops to 50 psi when hot faucets open then increases back to 85-90 psi. I think the tank will help, but an old school plumber told me to try a tee installed w/ a 12"-18" capped pipe ( hammer arrester) on the cold water supply. Any thoughts?
thanks
robbz
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robbz
Member
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Posted: Sun Aug 10th, 2008 06:51 pm |
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ps
HWT set @ 130 F. at faucets 120 f.
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eleent
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Posted: Sun Aug 10th, 2008 07:03 pm |
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Hello: You may have high pressure because the reducer is failing. Put your gauge on a bibb, turn the heater to pilot. Run water so the pressure drops, then watch the gauge. If it creeps back up to 80 psi, you know it has nothing to do with the heater. If it stays at 50 psi for say ten minutes, turn the heater back on and make it fire. Watch the gauge. If it goes up to the higher pressure in only a few minutes, it's thermal expansion. I'll add, you may have both problems and that would mean a new reducer and an expansion tank.
The device the plumber described is for water hammer. It won't help here. If water hammer is a problem, install the device made for it. In the old style described, air is absorbed into the water and the system needs to be drained periodically to put air back into the pipe, which people, being people, don't usually do 
Yours, Larry
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Ej
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| Joined: | Thu Aug 24th, 2006 |
| Location: | USA |
| Posts: | 161 |
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Posted: Sun Aug 10th, 2008 08:36 pm |
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| As Larry said, Your PRV could be bad even if it is still regulating properly. Most PRV valves have a bypass feature that permits the flow of water back through the valve into the main when pressures, due to thermal expansion on the outlet side of the valve, exceed the pressure in the main. Corrosion inside of the valve can cause this to happen to many 8-12 year old PRVs. Most bypasses will not work when the pressure is in the 140-150 psi range. Last edited on Sun Aug 10th, 2008 08:39 pm by Ej
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