Pressure differential - potential issue?

josha5690

Member
Jul 9, 2017
12
Alto, MI
I have a Pentair Optiflow 1HP pump with a Sparco hi-rate sand filter on a 28' above ground doughboy. I have noticed lately I am having a hard time keeping a prime on the pump especially when vacuuming. I can only vacuum for about 2-3 minutes and the pump loses its prime and most all suction. So I am trying to figure out if this is expected, if this is something I am doing wrong, or if there is a potential bigger issue I should consider or investigate.

In all of this testing I have disconnected our Polaris cleaner. I have turned the pump off, set the filter to recirculate and powered it back on. At that point the pressure shows 9 PSI. If I set the filter to filter and have just backwashed and cleaned everything, the pressure shows 11.5 PSI. On both recirculate and filter at those pressures, the return blows water back into the pool with a fair amount of force. If I vacuum for a small amount of time (2 minutes) or let the pool filter run for a day or two, the pressure will climb up to about 14 and at that point there is effectively no return into the pool, and the pump starts losing its prime and no water is really being pulled into the pump. If I then change back to recirculate everything goes back to 9 PSI and the return starts blowing again. The fact it works well on recirculate seems to tell me the pump is in good working order, I think.

I know from reading around here that pressures can vary quite a bit from pool to pool and system to system. What seems odd to me though is that after only about a 3 PSI increase in pressure, I effectively lose any filtration function. I see a lot of people saying it can be up to 10 PSI change before they worry about backwashing while others are at around 5. Is this 3 PSI change something to be concerned about or should I be checking into anything else within the system that could be causing some of this behavior, or is this "normal" and I just have to backwash multiple times an hour to be able to vacuum?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
21,381
Laughlin, NV
Sounds like your filter is doing its job, filtering out debris.

What does your water look like? What are your test results from your TF100?
 

josha5690

Member
Jul 9, 2017
12
Alto, MI
The water is still a little cloudy, still getting the water chemistry dialed in with SLAM, had 0 CYA so had to wait to get that delivered and get added.

I am definitely sucking up a lot of stuff when vacuuming, I just felt like only two minutes of vacuuming wasn't much and worried I was backwashing too much. But as long as it was expected, then I think I am ok, I just wanted to make sure that wasn't unreasonable.