The Classic Series UV's are ideal for ponds, aquariums, and water features. The Classic's rugged design has features that allow for quick installation and easy maintenance. Aqua Ultraviolet UV's will clear your water in 3 to 5 days sometimes overnight and keep it that way. The Classic 15W will sterilize up to 500 gallons of fresh water or 75 gallons of salt water. High quality quartz sleeve allows for a 99.9% transmission rate, and the included U.V. lamp lasts an impressive 14 months. Performance is guaranteed when sized, installed and operated according to manufacturer instructions. 3/4" Inlet / Outlet.