No flow

[TheHomeGuru]

Have an above ground pool, new 1hp Jacuzzi pump, new multisport valve on Hayward pro series s166t sand filter and just replaced the sand. Laterals are not cracked or clogged. Hardness is low 100, ph 7.2, cya low 20, ta 100, heavy cloudiness after SLAM and when filter wouldn't clear, tried flocculant which failed to settle debris. Been fighting this pool for a month.
Read other forums that were no help. Why does the flow reduce to nothing after a few minutes? If there was a clog, why would a backwash temporarily fix it?
I'm suspecting the multi port valve but what is going on? Have read "experts" say the pressure relief valve is clogged but this filter doesn't have one. Have read that air is getting in the suction side but there isn't a single bubble. Have read that pea gravel needs to be placed around the laterals but Hayward, and I don't advise this. Even when sand gets dirty, there will be some flow. This pool drops to zero.
Help!

 

[RDspaguy]

tried flocculant

There it is. When using floc, filter should be in recirculate and vacuumed to waste. Frankly, floc is a "when all else has failed" product to me. In 25 years, I have used it twice. Both times following wildfires in the area, as nothing else would get rid of the smoke. (Or whatever it was, I am still not really sure.)
Well, that's not true. I have used it many times in the backwash reclamation tank of the million gallon wave pool at a waterpark. Backwashing would use about 5000 gallons, which was pumped into a huge concrete tank, then floc'd and the clean water pumped back to the pool. Last 500 gallons or so of nastiness wasted out, tank washed out, and do it again next week.

 

[TheHomeGuru]

There it is. When using floc, filter should be in recirculate and vacuumed to waste. Frankly, floc is a "when all else has failed" product to me. In 25 years, I have used it twice. Both times following wildfires in the area, as nothing else would get rid of the smoke. (Or whatever it was, I am still not really sure.)
Well, that's not true. I have used it many times in the backwash reclamation tank of the million gallon wave pool at a waterpark. Backwashing would use about 5000 gallons, which was pumped into a huge concrete tank, then floc'd and the clean water pumped back to the pool. Last 500 gallons or so of nastiness wasted out, tank washed out, and do it again next week.

I use floc as a last resort as well. I used it after two weeks of trying to filter the dead algea. I did run it on recirculate for 24 hours and I did turn the pump off for another 24 hours. The next day, the pool was just as cloudy. And please, try to answer my question rather than give an unrelated anecdote. I'm getting frustrated here and don't read these forums for entertainment.
Thanks.

 

[RDspaguy]

Ok. I was saying the floc was what is causing your filter to clog. But I guess that is unrelated.
Good luck.

 

[TheHomeGuru]

Ok. I was saying the floc was what is causing your filter to clog. But I guess that is unrelated.
Good luck.

Thanks. You may be partially correct. But I think the new pump is overpowering the sand and driving the debris into the laterals. Checked the impeller and all hoses. No blockages so that leaves one possibility, the sand. The S166T filter has a 1.4 sq filter area and a 35 gpm rate. I think the 1hp Jacuzzi pump is pushing above that rate. Also, the pool volume is 19000 so according to recommendations I am seeing, this filter is undersized, though I have never seen a bigger filter on an above ground pool.
Put a new good oil filled pressure gauge on and it is reading 5-8 psi with no air in strainer. Seems low to me as if the water is just whisking through the sand as if it isn't present.
Sound plausible?