20'x40' vinyl liner pool, 23K gallons, filter: Hayward DE 3600 4820, 1hp single speed 1.65 V-Green VS motor, Circupool RJ-45 SWG, 1.5 inch PVC, 2 skimmers/1 main drain, 3 returns and 2 bubble jets @ stairs, and a partridge in a pair tree. testing: K-2006, Salt; K-1766, Test Strips; Aquachek 7. calculator: PoolMath