Ok, bear with me please.
Backstory, about 3 weeks ago:
Upgraded well pump to 15gpm, 1.5HP (15FA15S4-2W230) had a CSV125-60-1 (mfr. in 2021) installed about 5-10' below the pitless, and my existing 32 gallon tank adjusted for 50-70 psi with bladder set to about 48 psi. Pump is about 80-100' deep in a 120' well, with well yielding about 25 gpm. Pipe is 1" poly pipe, about 25-30' of pipe from pitless to well tank, no or little elevation change, with 3 elbows in poly pipe visible, possibly 1 more buried.
The CSV was only holding about 55/56 PSI (at 7-8 gpm) at the pressure tank but I figured because it was installed a about 5-10 feet below pitless and variation in the valve that this was acceptable. Then I noticed that with a 7.5 gpm irrigation zone running and taking a shower (~ 2 gpm mixed hot/cold) that the pressure wasn't as good. Checking the pressure gauge at the pump showed it at around 51 psi and sometimes 50 or even 49 psi.
Called the installer, had him come out today and we tried a bunch of stuff and couldn't land on anything.
Today, we observed the same behavior described above, pressure not maintained at 55 when demand approaches ~9-10 gpm.
* Keep in mind, irrigation and whole house water share about only 5' of 3/4 copper after the pressure tank, then the irrigation tees off on 3/4" pex with a 200 micron sediment filter, and the whole house goes to 3/4" pex and a 25 micron 10" whole house filter and branches out all over the house.
We moved the existing CSV up, about 2 feet below the pitless and were able to see the maintained pressure at about 57-58 psi but it would still drop ~5 psi when demand would go from ~8 to ~10 gpm.
We then swapped the CSV out for a straight coupling and ran the irrigation and shower (~ 10 gpm). The tank was able to keep up and would cycle on at 50 psi for about 1-2 min before shutting off at 70 psi. Then repeat. Typical.
We then installed a different CSV125-60-1 (mfr. in 2022) and saw similar but also other unexpected behavior.
At 8 gpm, pressure would climb to 67 fairly quickly, then slowly reach 70 and shut the pump off. Drain the tank, and repeat. Did the same thing with shower only (at 2 gpm). At this point we were at a loss and the well guy left and we said we would reassess and see what else can be done.
After he left, I ran the water and timed the behavior under various conditions.
(all below time deltas are from previous delta, not cumulative).
Irrigation running (~8 gpm), tank drains, then pump kicks on at 50 psi
+ 1 min - 60 psi
+ 4 min - 67 psi and holding
Turn on shower @ ~2 gpm (9.5-10 gpm total).
+ 30 sec - drops to 62 psi (Then I notice that the pipe and pressure gauge shudders briefly)
+ 20 sec - 70 psi and pump shuts off
+ 40 sec - Tank draws down 70-50 psi. Pump turns on.
+ 1.5 min - Rises to 56 psi. Holds at 56 with ~9.0-9.5 gpm (slightly lower due to lower pressure).
Turn off shower, Irrigation only (~8 gpm)
+ 20 sec - 58 psi.
+ 1.5 min - 62 psi. Holds at 62 psi.
Open other irrigation zones to max out flow. (~10 gpm).
+ 30 sec - 58 psi.
+ 30 sec - 57 psi
+ 30 sec - 56 psi
+ 1.5 min - 55 psi. (Now at ~9.5 gpm due to lower pressure). Holds at 55 psi.
Shut off extra zones and only leave (~8 gpm zone on)
+ 20 sec - 57 psi
+ 1 min - 60 psi
+ 2 min - 62 psi. Holds at 62 psi.
Irrigation shuts off (0 gpm demand)
+ 15 sec - Tank fills from 62-70 psi and pump shuts off (this is too quick, no?).
Turn on irrigation again (~8 gpm)
+ 45 sec - tank draws down from 70-50 psi, pump turns on.
+ 30 sec - 56 psi
+ 45 sec - 58 psi
+ 1.5 min - 60 psi
+ 2 min - 62 psi. Holds at 62.
Turn on shower (9-10 gpm)
+ 30 sec - 56 psi
+ 1 min - 55 psi
+ 2 min - hair over 54 psi. holds here.
Turn off shower. Irrigation still running (~8 gpm)
+ 30 sec - 57 psi
+ 30 sec - 59 psi
+ 30 sec - 60 psi
+ 2 min - 62 psi. holds at 62.
Irrigation turns off (0 gpm demand)
+ 15 sec - Tank fills from 62-70 psi and pump shuts off.
I'm not an expert in plumbing, pumps, fluid dynamics, but I can read and comprehend things. From everything I've read, and I've read a lot, there shouldn't be a 5+ PSI difference when going from 8-10 gpm. 1" Poly only drops about 2.8 psi per 100 ft of pipe @ 10 gpm due to friction loss.
Also, when demand is turned off, it's supposed to fill the tank at 1 gpm and is filling and shutting off too quickly.
I'd love if the CSV could maintain the 62 psi at various demands. But the plan is to eventually upsize the mainline to irrigation and put out 10-12 gpm on each zone. I upgraded the pump so that I could do that and maintain enough water for home use. That pump at that depth should have no issue putting out 15-17 gpm from what I understand.
Any help would be much appreciated.
