crystals at bottom of pool that dry into white flakes HELP!!


In The Industry
Jul 30, 2010
Hello everyone i just joined the forum. I have started cleaning pools and have been doing this for about a month now. My brother and i are working a guys accounts and will be taking over them. currently we have a big pool right now that has this crystal like stuff at the bottom of the pool that accumulates over time. Its in the pool every week when i go to service the pool. When i pull it out of the pool and let it dry out it turns into a white flake when i rub it between my fingers it turns into a kind of white powder so the stuff is soft. Now the stuff started to show up when my boss drained the pool and filled it back up. but it didn't start to show up until about 6 to 7 months later. I took it to my pool store that i get all my pool supplies from and surprisingly non of them really seemed to know what it was. but what they said it most likely was was calcium but they weren't sure. I've done a ton of research for this and have only found a few people with the same problem but never really got a forward answer on how to fix it. one of the things that i read was that it might be a fungus of some sort. I know its not DE either. So before i go and try anything i wanted to see if i might be able to find someone that has or had the same problem and has fixed it. If you guys could help me out that would be great because the people i talk to don't seem to have any idea and i would hate to loose this customer.



TFP Expert
LifeTime Supporter
Mar 29, 2007
Coastalish 'down easter'
Welcome to TFP!!

Before we can even start guessing as to what this is, we need a full set of water test numbers :cool:

As you are in the business, like me, I strongly suggest the TF 100 kit (see my sig) - I stopped using the other kits a few years ago (though the Taylor K 2006 C is a very decent kit) the only thing I suppliment the TF 100 kit with is the acid/ base demand test from the K 2005/ 6. The magnetic stirrer is a great time saving add on!

It's a pleasure to see you come here so that you can better take care of your customer's pools :goodjob:


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
I'd look at the water numbers first. If it's something like the CH is 1400 and the CSI is 2.3... you pretty much have the answer.

If you're going into business, you ought to check the laws. I don't know where you are, but I know that Los Angeles County requires Pool Service Technicians to be licensed.


TFP Expert
LifeTime Supporter
Nov 5, 2008
Are the crystals clear and jelly-like when wet? Then very much smaller when dry? Do they have a baby in diapers or let a baby in diapers into the pool?

If so, it may be water absorbing crystals from baby diapers. This is also sold as additive to potting soil to help soil hold water longer. The stuff comes in various grades so one type may be fine powder when dry and the other more like coarse salt. [edit]

One busted diaper can let loose a lot of this stuff. I think each diaper can hold something like 4 cups of fully expanded polymer crystals based on when I let my kid into a pool with one of those one many years ago. If there is a Polaris be sure to clean the small inlet screen there and anywhere else such stuff might be stuck in filters and such.

We have seen a post about this once before. Search (top banner Search) for diaper might turn it up. [Edit - it was in the one titled "Mush" and the photos are not there now.]


Well-known member
Jan 25, 2010
we've had a busted diaper in the pool before- it's a holy mess to clean up. Could be calcium, too.


New member
Aug 18, 2010
I found this thread just now looking for the exact same thing. I have the EXACT thing you described in my pool. I vacuum them all gone and they come back. It's a while flakey thing that turns powder like (salt) when it dries if you rub it. I had my water fully tested and it looks great. The pool looks great as well, but they keep accumulating in this one spot in the deep end.

Did you resolve this or find out what they are? I am in FL with a non-screened pool. Thanks for anymore info anyone!

Edit - called and got my pool #'s from Monday water test:

Alk: 100
Salt 3200
stabalizer: 60


TFP Expert
LifeTime Supporter
Nov 5, 2008
I think the test would be if you collect the salt-like crystals and drip water onto them slowly, maybe 3x volume of crystals. If you see it swell and turn into a clear jelly substance, it is probably these water absorbing polymer crystals.

You can see a greatly magnified photo here

As for how to rid the pool, I think the last fellow just kept cleaning it out of the cart filter. If you vac a lot of it to a cart filter I suspect it will clog up and could bust the filter, I recall one fellow had that problem. I wonder if sending it through a sand filter would crush the particles so that you might not be able to get it removed.

If it were my pool, I'd probably let it settle to the bottom every few days and take a wire colander from the kitchen to scoop it up if I could. Or if you can vac to waste, maybe.

Question is, where is it in the pool? Could be in the pool, where it will migrate to the deep end. Could have a lot in the filter already so that needs to be cleaned regularly. A polaris ought to pick up a lot of the gel. Not sure if sweeping would collect it faster.

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