Why does my pool keep getting sand at the bottom even though no one tracks anything in?

[Manikshaw]

For the past week I’ve noticed small piles of what looks like sand collecting on the bottom of my pool. We don’t have a sand filter only a cartridge system and no one swims with sand on their feet. I vacuum it up and by the next day it’s back again in the same spots. Not sure if it’s insects, dust or something else blowing in. Anyone run into this mystery debris before?

 

[Zephyr]

For the past week I’ve noticed small piles of what looks like sand collecting on the bottom of my pool. We don’t have a sand filter only a cartridge system and no one swims with sand on their feet. I vacuum it up and by the next day it’s back again in the same spots. Not sure if it’s insects, dust or something else blowing in. Anyone run into this mystery debris before?

If it keeps coming back in little piles it might be dead algae rather than sand. It looks similar and settles fast. Try brushing the spots if it poofs into a cloud it’s algae, not dirt.

 

[Freddie]

For the past week I’ve noticed small piles of what looks like sand collecting on the bottom of my pool. We don’t have a sand filter only a cartridge system and no one swims with sand on their feet. I vacuum it up and by the next day it’s back again in the same spots. Not sure if it’s insects, dust or something else blowing in. Anyone run into this mystery debris before?

Could be pollen depending on where you live. Mine looks exactly like tan-colored sand when it settles. Cartridge filters catch most of it but windy days bring it right back.

 

[syedsam]

For the past week I’ve noticed small piles of what looks like sand collecting on the bottom of my pool. We don’t have a sand filter only a cartridge system and no one swims with sand on their feet. I vacuum it up and by the next day it’s back again in the same spots. Not sure if it’s insects, dust or something else blowing in. Anyone run into this mystery debris before?

Also check your return jets. Even though you don’t have a sand filter sometimes fine dirt backflows from the plumbing if the pump shuts off suddenly. I had this issue when my check valve was sticking.

 

[Manikshaw]

Brushing did make it cloud up, so maybe it is dead algae like you said. I’ll run a shock treatment and see if it stops showing up. Thanks for the help.

 

[Diego Rodriguez]

If you’re on a cartridge system and it still looks like “sand,” most of the time it’s dead algae or pollen settling, not actual sand. I’d brush those spots: if it puffs into a cloud, it’s algae. If it doesn’t, it could be windblown pollen/dust, so check your return jet direction so it’s not piling up in the same spots. And it’s worth checking the returns too, sometimes fine debris can backflow from the plumbing if a valve isn’t sealing right.

 

[Ashley Hernandez]

If you brush it and it puffs into a “cloud,” it’s usually dead algae, not sand. I’d shock and run the pump longer for 1 to 2 days, then vacuum slowly. If it still comes back, check your return jet direction and make sure you’re not getting any backflow when the pump shuts off.

 

[Matthew Collins]

I had a weird version of this a couple summers ago and it really did look like someone sprinkled sand in the pool overnight. Turned out it wasn’t sand at all, it was really fine dirt and organic dust blowing in at night and settling in the same spots because of how the circulation pattern worked.

What tipped me off was that it always showed up in two little piles near the deep end where the floor slope starts. My returns were aimed mostly across the surface, so the bottom of the pool was kind of a slow “dead flow” area. When the pump shut off overnight everything just settled there. Once the pump started again it didn’t fully lift that fine stuff back up to the filter.

I ended up slightly angling one return downward to push some movement across the floor and also cleaned my cartridges because the filter pressure had crept about 5 psi above my normal clean reading. After that the dust stopped collecting in those piles nearly as much. Pools can get these weird circulation pockets where debris just likes to park itself. Anyone else notice certain spots on the floor always collecting stuff first?