Need help with a problem. Precipitate on bottom of pool.


Well-known member
May 26, 2007
Hi All,
I recently installed a Pentair Whisperflo 3/4 HP pump and a 48sqft FNS plus DE filter. I went on vacation 1 day after the install. I returned 4 days later to a pool that was 90 degrees (when I left it was 70) and a very hazy pool. Turns out while I was gone one of my relatives came over, turned the heater on and didn't shut it off. Compound the high pool temp with 95 degree temps and I had zero chlorine. Last night I added 3 gallons of bleach and it brought the FC to about 8ppm.

Now the pool is clear but I develop sediment on the bottom of the pool. I vaccum it up with my blue diamond but it returns a few hours later. What is this precipitate? I am thinking it's either dead algae or something, even though the pool wasn't green or DE.

I am concerned because the pump is on a timer and if the heater was on when the pump shut off could it have damaged the grids? I plan to backwash tomorrow and inspect the grids but the filter is brand new so I am hoping not to find anything unusual.

Any advice appreciated.



TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
It could easily be dust, though there are many other possibilites. After a storm we get dust blown into the pool that takes a couple of days to slowly settle on the bottom.

Most modern heaters will shut off when there is insufficent flow without damaging anything. Some people have had melted pipes when the heater is running and the pump shuts down, but that is getting less common with newer heater designs.


Well-known member
May 26, 2007
Well I took the filter apart and all looked OK although I really don't know what I am looking at :) No tears or holes which I guess is what 's important. Going to recharge and see what happens. I have a new Sta-rite heater too. I was just concerned that the hot water may have damaged the filter upon shutdown.

I also noticed that my chlorine feeder has some air bubbles in the line which enters before the pump. Could the small amount of air cause DE to blow into the pool? I didn't think so but thought I'd ask anyway.