PRV Needs Thermal Tank? - General DIY Discussions - DIY Chatroom Home Improvement Forum

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Old 11-18-2015, 12:57 PM   #1
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PRV needs thermal tank?

I recently purchased a house and the inspectors said I needed to install a Pressure Reducing Valve as the pressure measure at the spigot outside was 80 psi. I've measured it at 78-80 pretty consistently since we moved in.

So, I have a few questions:
-Is 80 psi high enough to necessitate installing a PRV?
-If I install a PRV, do I then need to install a thermal expansion tank on my water heater or are the two not always necessary together?

Thanks a lot for the help!
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Old 11-18-2015, 01:07 PM   #2
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80 psi is at the upper end of what is generally acceptable pressure inside the house. Typically the pressure is 60 psi or lower. Check out this link for some discussion about typical pressure in a house

Some pressure reducing valves incorporate a backflow preventer. For example, the pressure reducing valve that feeds water to my boiler also acts as a backflow preventer. If you have a backflow preventer in your system, you need an expansion tank, since there will be no place for water to expand to when it heats up. If there is no backflow preventer, then the water can expand into the city water supply system, so an expansion tank would not be needed. Your local plumbing inspector can tell you if you need a backflow preventer incorporated into your pressure reducing valve, assuming you decide to install one.
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