Why do tiny sand-like particles keep settling on the bottom even after I vacuum?

[syedsam]

I keep getting these tiny sand looking particles on the bottom of my pool. I vacuum them up and the pool looks perfect but by the next day the same stuff shows up again. It doesn’t feel gritty like real sand more like super fine dust. My filter pressure seems normal so I’m not sure if it’s coming from the filter, the environment or something else. Anyone seen this before?

 

[Freddie]

I keep getting these tiny sand looking particles on the bottom of my pool. I vacuum them up and the pool looks perfect but by the next day the same stuff shows up again. It doesn’t feel gritty like real sand more like super fine dust. My filter pressure seems normal so I’m not sure if it’s coming from the filter, the environment or something else. Anyone seen this before?

If it keeps returning after vacuuming, it could be dead algae. It settles like dust and reappears fast. If you can brush it and it puffs into a cloud that’s usually the giveaway.

 

[Zephyr]

I keep getting these tiny sand looking particles on the bottom of my pool. I vacuum them up and the pool looks perfect but by the next day the same stuff shows up again. It doesn’t feel gritty like real sand more like super fine dust. My filter pressure seems normal so I’m not sure if it’s coming from the filter, the environment or something else. Anyone seen this before?

Check for a cracked lateral in your sand filter if you have one. Fine sand can leak back into the pool and it looks exactly like what you’re describing. Happens more often than people think.

 

[Manikshaw]

I keep getting these tiny sand looking particles on the bottom of my pool. I vacuum them up and the pool looks perfect but by the next day the same stuff shows up again. It doesn’t feel gritty like real sand more like super fine dust. My filter pressure seems normal so I’m not sure if it’s coming from the filter, the environment or something else. Anyone seen this before?

Could also be pollen if you live in a windy area. Mine looks like yellowish dust on the floor and returns every day during heavy pollen season. Clarifier helped my filter catch more of it.

 

[syedsam]

I’ll try the “brush test” to see if it clouds up. If it does it’s probably dead algae. If not, I’ll check my sand filter. Appreciate all the tips.

 

[Diego Rodriguez]

I’ve seen this before. Try the “brush test”: if you brush it and it puffs into a cloud, it’s usually dead algae. But if it stays like fine grains and settles fast again, check your sand filter (a lateral issue can let sand back into the pool) or it could be pollen if it’s that season. Give that a shot first.

 

[Ashley Hernandez]

I’d start with the “brush test.” If you brush it and it puffs into a cloud, it’s usually dead algae, so shock and run the pump longer. If it stays gritty and settles fast again, it’s probably dust/pollen, or (if you have a sand filter) sand is slipping through, so check the inside of the filter.

 

[Matthew Collins]

One other thing I’d look at is what happens when the pump shuts off at night. I had this exact “dust keeps coming back” situation and it turned out the circulation was just a little too weak to keep the fine stuff suspended long enough for the filter to grab it. During the day it looked perfect, then overnight everything would slowly settle to the floor again.

In my case the pump schedule was pretty short and the return jets were aimed slightly downward, so there wasn’t much surface movement or circulation across the floor. I angled the returns a bit to create more of a slow circular flow and bumped the runtime a couple extra hours. That alone reduced the amount of dust settling overnight.

Also keep an eye on your filter pressure relative to its normal clean number. Mine was only about 4–5 psi above baseline so it looked “normal”, but the cartridges were actually starting to get a bit blinded with fine debris. After a proper cleaning the pool started catching that dust way better and I wasn’t vacuuming every morning anymore. Pools can be annoying like that, everything tests fine but the circulation just isn’t quite dialed in.