Normal gauge pressure but low flow

[BikerBill]

For the last several days (and probably longer) I've noticed the water flow into my pool has dropped noticeably: very little surface disturbance near sidewall nozzles, less pressure from the floor jets. The pressure gauge on the filter tank shows its normal 28-30 psi. I've cleaned the two skimmer baskets and the pump strainer--not much debris so no change after cleaning. The pump motor is making no unusual noises. If there were an obstruction after the pump I'd expect to see the pressure rise, but that's not the case. It seems that would point to an obstruction upstream of the pump. I don't know how the intake piping could get clogged as I never run the pump without skimmer or strainer baskets. But I'm sure there's a way. Moles building lots of little subterranean Jacuzzis?

Some details: Pentair Whisper Flo 1.5 HP pump, Pentair FNS Plus DE filter. Gunnite inground pool with in-floor cleaning system. Equipment is 12 years old.

What do I look for next?

 

[Jimrahbe]

Bill,

Put the filter MVP into the recirculate mode and see what happens.. If flow returns to normal, then your filter is dirty.

Thanks,

Jim R.

 

[BikerBill]

Jim,

I assume you meant MPV (multiport valve), not MVP. Any way, my system does not have such a valve. It has a two position backwash valve with a T-handle that you push-pull and turn. There's another valve which allows me to use just the skimmers, just the main drain, or both. But I don't see how can I set it up to recirculate. Am I missing something here?

I've been doing some Googling and see that a clogged impeller may cause this problem. Does that happen much in actual practice?

Thanks,

Bill