Runs with Bison
Member
Okay, I've got what I believe is a problem with the old Watts PRV in my home. It is still functioning and not leaking through to full supply pressure, but it can't seem to maintain dynamic pressure within reasonable range of the static pressure. As soon as I open even the slightest flow the pressure drops off about 10 psi...and by slightest I mean 1/4 gpm...bucket tested. At 1-2 gpm it loses about 17 psi.
Typical data set is: 1.2 gpm flow (bucket test)
Municipal supply ~118 psig
Static pressure (no flow) 75 psig.
Pressure with flow 58 psig.
PRV is a Watts N35B, 3/4" with female threads, about 15 years old. Spec curve can be found at http://www.fs.fed.us/fire/sdtdc/02511304/fig2.pdf The curve suggests that at 1.2 gpm the pressure drop should only be about 1-2 psi.
The reason it is a problem is I seem to be getting low supply pressure to an upstairs shower head that is already giving up nearly 8 psi in vertical rise. Other fixtures on that level can handle it, but perhaps not the shower head which is underperforming. I raised the static setting to 82 psig at the PRV, measured 66 psi dynamic at 1.25 gpm flow (bucket test.) I've tweaked it a little past this now and will retest with bucket in the morning, but this is at the adjustment limit and outside of specs anyway. It's a low flow showerhead, but 1.25 gpm is at least .25 gpm lower than expected and appears to be detrimental to performance. The old 2.5 gpm wasn't starved for water, so the 1.5 gpm should have even less problems. Could be a defective showerhead, but the PRV performance has my attention at the moment.
Am I wrong to think that it should be possible to get very little dynamic loss at such low flows if the regulator was functioning correctly? It's strange that I've had no flow issues in the home with multiple things running despite the PRV dropping the pressure so much below set point. I did note that before I started adjusting originally (shortly before the showerhead was replaced) the PRV was at the limit of adjustment, upper 80's psi. I first adjusted it down to 75 static and everything seemed happy enough, although I could tell pressure was lower. Then I installed the new showerhead.
There is no appreciable lime buildup in the lines I've opened so far, (and I've replaced several plumbing fixtures in the home.) There are no leakers. Unfortunately, my understanding is that the N35B is obsolete and a bear to service in place, plus it might not be repairable. So I'm considering replacing it with the Watts 25AUB in 3/4". Am I missing something obvious?
Typical data set is: 1.2 gpm flow (bucket test)
Municipal supply ~118 psig
Static pressure (no flow) 75 psig.
Pressure with flow 58 psig.
PRV is a Watts N35B, 3/4" with female threads, about 15 years old. Spec curve can be found at http://www.fs.fed.us/fire/sdtdc/02511304/fig2.pdf The curve suggests that at 1.2 gpm the pressure drop should only be about 1-2 psi.
The reason it is a problem is I seem to be getting low supply pressure to an upstairs shower head that is already giving up nearly 8 psi in vertical rise. Other fixtures on that level can handle it, but perhaps not the shower head which is underperforming. I raised the static setting to 82 psig at the PRV, measured 66 psi dynamic at 1.25 gpm flow (bucket test.) I've tweaked it a little past this now and will retest with bucket in the morning, but this is at the adjustment limit and outside of specs anyway. It's a low flow showerhead, but 1.25 gpm is at least .25 gpm lower than expected and appears to be detrimental to performance. The old 2.5 gpm wasn't starved for water, so the 1.5 gpm should have even less problems. Could be a defective showerhead, but the PRV performance has my attention at the moment.
Am I wrong to think that it should be possible to get very little dynamic loss at such low flows if the regulator was functioning correctly? It's strange that I've had no flow issues in the home with multiple things running despite the PRV dropping the pressure so much below set point. I did note that before I started adjusting originally (shortly before the showerhead was replaced) the PRV was at the limit of adjustment, upper 80's psi. I first adjusted it down to 75 static and everything seemed happy enough, although I could tell pressure was lower. Then I installed the new showerhead.
There is no appreciable lime buildup in the lines I've opened so far, (and I've replaced several plumbing fixtures in the home.) There are no leakers. Unfortunately, my understanding is that the N35B is obsolete and a bear to service in place, plus it might not be repairable. So I'm considering replacing it with the Watts 25AUB in 3/4". Am I missing something obvious?