after our pool is cleaned, an hour later there will be sand on the bottom of the pool again. What is the prob?

serendipity pools

You have a broken lateral in your filter. If you look you will see that the sand is located in lines in front of all of your return jets in the pool. You need to have your filter serviced. The sand will need to be removed, the broken lateral replaced, and fresh new sand installed in your filter.

In the worst case scenario your filter will be too old to find replacement parts for and will need to be replaced all together.

I hope this information is helpful.

Steve Goodale
Serendipity Pools