high water pressure

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high water pressure

Author: bbspot (CA)

I have 120 psi water pressure at my new house.
I installed a new PRV and it did not help. I turned off my water heater and drained all the hot water and it still did not help. I don't have an expansion tank.
But when I turn on the sprinklers, the pressure drops to 60-70. When I turn off the sprinklers, it jumps to 180, and slowly drops to 120. I also have a water hammer at this point.
What is going on?

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Re: high water pressure
Author: packy (MA) either the new PRV is defective or it was not installed correctly. you will also new an expansion tank.
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Re: high water pressure

Author: bbspot (CA)

It turns out that all my outside hose bibs are on a separate branch before the PRV.

After I turned off the water heater, I tested my washing machine and it was 78 psi.
But once I turned it back on, it jumped back to 100+ psi. So I guess that means I need a expansion tank.
Would the expansion tank help lower my psi to 60?

The next question is do I need a PRV for the branch? Would I need a high capacity PRV (expensive)? And would this solve my water hammer issue?

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Re: high water pressure
Author: KCRoto (MO) I would suggest getting a licensed plumber on site to assess the situation. He should be able to determine the proper parts needed to do the job
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Re: high water pressure
Author: packy (MA) an expansion tank will not reduce the water pressure below the 78PSI you have with the water heater turned off. it will keep the water pressure from spiking upwards when the heater is working. the PRV is adjustable and it is pretty simple to lower the pressure.
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