21,000 gallon, kidney shaped, in ground pool, 5.5 ft deep max, vinyl lining, approx 12 years old as of 2018, Sta-Rite 3 cartridge filter pump, Sta-Rite Maxi-Therm 333 pool heater, copper ionizer, in-line chlorinator, on well water so rain is primary source of refill water. Central Pennsylvania, USA