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Author:
Colew0pi (PA)
Long story short…had really high pressure coming into home, around 180 psi. Had PRV changes and then added a second unit to run in tandem. Set them at 52. Still getting spikes several times a day up to 120. As soon as I run laundry faucet for a few seconds, pressure goes right back to normal. Wouldn’t worry about it but as soon as it spikes, the first toilet or hose bib I turn on, the hammering starts. Can you help?
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Author:
steve (CA)
Do you have an expansion tank installed?
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Author:
Colew0pi (PA)
Hey Steve! Yes, we have an expansion tank. I checked the pressure in it yesterday and it was reading 62 and the PRVs are set at 52, so I let some pressure out to get it down to 52. It’s been about 16 hours now and the pressure is holding. The red line on the gauge has spiked above 80 but black line is holding steady. Hoping it’s not just taking a break….lol! Does any of that make sense?
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Author:
packy (MA)
turn the water off and open a faucet to get the pressure to about zero. lower the expansion tank pressure to 15 or even less.
remember that the expansion tank has nothing to do with helping the water flow. it absorbs the expanding water when the water heater heats the water.
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Author:
Colew0pi (PA)
Thanks so much for the note. Makes total sense. I only took it down to the 52 because the Internet seems to be full of plumbing geniuses that say it has to match the PRV settings. So far, it’s been holding steady. Quick additional question, so when the red needle spikes and the black remains in range, that spike is being absorbed by the expansion tank?
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Author:
packy (MA)
no... the tank absorbs any expansion thus preventing spikes.
also, the pressure on the street may rise slightly at night when water usage is at a minimum.
but it won't suddenly spike. it doesn't work like that.
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Author:
Colew0pi (PA)
Got it, I think. Just wasn’t sure why that red needle would jump at times. Good news is, since I let some pressure out of the expansion tank, the black needle doesn’t follow it!
Thanks for the info.
Really appreciate it. Should have checked into this site months and two plumbers ago!
Edited 1 times.
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