Wide PSI Fluctuation of Static Water Pressure, is this Normal?

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profhoff

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Plumber replaced pressure reducing valve (PRV) because of Moen Flo alert that PSI was over 80 for 24 hours. I then monitored PSI with my Moen Flo smart water shutoff for the past three days (see chart). First 24 hours PSI varied 2 PSI. Second 24 hours PSI varied 9 PSI. Third 24 hours PSI went up over 15 PSI and is coming down now.

Relevant details:
  • PSI peaks all three days around 8am, but peaks are getting higher.
  • PSI bottoms out mid-afternoon, same level each day.
  • No one was in the house during these 3 days, and zero water was run during this time.
  • House has two tankless water heaters. They only operate when water is run. Since no water was run, thermal expansion should not be an issue.
  • This is the 3rd replacement PRV value. Two previous PRV values had pressure spikes.
  • There is a whole house Lifesource filter after the PRV valve and before the Moen Flo. Plumber bypassed the Lifesource to take it out of the equation.
Any theories about what is going on here?

Why is PSI oscillating up and down without any water use, now with a 15 point swing? If municipal water supply pressure is increasing over night as community use goes down, would a PRV value allow a 15 point low-high PSI range? How tight of a range should a PRV control static water pressure?
Moen Flo PSI.png
 

Breplum

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PRV only prevent over-pressure. So, if set at 75psi or so, it is doing its job.
Hard to guess/know why you are getting such drops.
 

Jeff H Young

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Well its interesting and a mystery that your pressure fluctuates. If I put a new regulator in and my water pressure never dipped below 60 but often went over 70 Id lower the pressure . 75 or 80 isnt a problem per say but I sure dont want 80 or even 75
you brought up changing regulators that this is your 3rd ok 3rd one in a month? 3rd in a decade ? how old is your current regulator ?
Im not sure a 15 psi differance is that unusual I probebly wouldnt worry about it PRV valves are known to creep up in pressure im not sure a good one would creep that much or be expected to be able to go days without creeping . Ive never been that picky or investigated it that thouroughly .
Profhoff I dont know which brand and model you have but you can easily get in touch with thier customer service with this information and they can tell you if its normal Can you call them find out and post the answer Im curious what they tell you I think they might say its normal but dont know but sure like to hear back on it !
 

John Gayewski

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Pressure fluctuating is normal on municipal water. The water company should know by how much it normally fluctuates.
 

Jeff H Young

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Pressure fluctuating is normal on municipal water. The water company should know by how much it normally fluctuates.
Yes she should monitor that pressure as well! Myself I wouldnt worry about it . But if plumber sets pressure at 60 it will probebly holdy hold at 60 Probebly has it set at 75 but if the city water pressure is down at 60 part of day the house pressure will drop thus the fluctuation .
 

profhoff

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Municipal water company guy came out and measured pressure at street. He claims pressure is a steady 94-96 PSI and insists it never fluctuates!
 

Jeff H Young

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Municipal water company guy came out and measured pressure at street. He claims pressure is a steady 94-96 PSI and insists it never fluctuate
Ok so every day the pressure drops to 60 at 3 pm and its nothing to do with water district..... Maybe the water boy knows maybe not is there any confirmation of incoming pressure or just his hearsay ? install a guage upstream of regulator and check at various times .
a bit odd but if you want to unlock mystery youll probebly have to get involved .. I dont belive the regulator is working perfect , there is no fluctuation in pressure , and there is no water being used for 3 days at a time . somewhere in that mix more is going on and some info is incorrect. So your home work is confirm the incoming pressure at at least 10 times a day spread out as best you can.
 
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