25 year pool is 21x40 vinyl inground, holds approx. 30,000 gals. Haywood Pro series High rate sand filter holds 300 lbs sand. We have a Haywood RS 1500 series pump - 1 1/2 horsepower, Two skimmers, main drain, 4 returns, city water. Polaris 380 vac. TF 100 test kit. Monthly - Smile,Amazon contributor since Aug. 2017.