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:
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?
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.
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?
