We have a new unite IG pool with plaster surface. After the plaster was done the PB started the fill process. I brushed daily but after about three days we noticed that some sand deposits had formed on the bottom. They look like dirt that you normally could just brush or vacuum up. However, they won't come up. They seem almost bonded to the plaster surface. The pH of the pool did spike towards 8.6 at times before I could add acid to get it down. The PB is going to have his guy come over and check it out.
Any ideas on what needs to be done to get rid of these sand deposits? Thanks.