PoolDoc, I don't think I received a "how-to" manual when I got the pool installed. The instructions on the filter system do not give any specific cleaning solution to use. The installer instructed me to spray the filters clean with water. I basically do as I am told. The psi for clean filters is 10 on my meter. Anything over 20 is dirty. I have been cleaning the filters at least once a week. 35,000 gallon pool w/ 4 filter elements and the pool is 5 months old. Before I gave a 50/50 part muriatic bath, the psi would go no lower than 30 psi. After the bath the psi was 15 but worked its way back to 20 within a few days. Could you please tell me what the first thing to clean with is? Thank you. Brian