I keep getting white circular clumps on the bottom of the pool. When you brush them they dissolve into a powder. Chlorine numbers are good and show no combined chlorine. I brushed/vacuumed and brought the pool up to shock level anyway to see if it would help. Passed the overnight loss test and still showed no combined chlorine, but the spots came back. So its not algae, right? My calcium hardness test is not high (about 60), so could it be calcium deposits? We do have metal in our water and use sequestrant for that. The pH was high at about 8, but I have brought that down to 7.4 with MA. I vacuumed to waste today (3 times) and brushed and the bottom is clear at the moment, but I don't know what else to do if it comes back again. WHAT IS THIS STUFF??
White clumps on bottom of pool
- Thread starter southgaamy
- Start date
full set, please 
I am going to guess pollen or you maybe you have a low level algae bloom (although you pretty much checked this already).
I was just reading threads on pollen trying to see if that could be the problem. I think it just might be, because the pollen is bad in this area and we have a LOT of pine trees. You can see the pollen on the surface of the water, but I wasn't sure that it would collect on the bottom of the pool. Is there anything that helps control the pollen because it stays around for months in our area?
Use a skimmer sock or a knee high over the basket in your skimmer. I use the knee high. Their cheaper. It will catch a lot of pollen and other stuff. Just make sure you check it pretty often during high pollen days and clean it out or replace with new. They can restrict flow to your pump when they get full of junk.
It's best to set up an account on a host site like photobucket, flickr or similar. Upload them to an album, then copy the IMG link to it and paste it in the same box you post in.
Also, if you can capture some for testing (skimmer sock), if it is pollen will feel squishy. Sand/dirt feels gritty & algae feels slimy.