20 Gallon Capacity, Horizontal, Pressure Pump Tank, Designed To Meet The Requirements Of & Are Listed By The National Sanitation Foundation NSF Under ANSI /NSF STD 61, The Butyl Diaphragm Has Seamless Construction & Is Designed To Flex Rather Than Stretch & Crease Like Bladder Tanks, The Polypropylene Liner For The Water Reservoir Will Not Flake, Chip, Crack Or Peel & Does Not Impart Taste & Odor To The Water, Diaphragm, Liner Isolate Water From Contact With Deep Drawn Steel Domed Shell, Twice As Strong As Rolled Steel Shell Of Same Thickness, A High Gloss Enamel Finish Protects Tank From The Elements, Pre-Charged To 25 PSI, Usable Water Drawdown @ 30-50 PSI, 6.1 US Gallons, 1" Male Pipe Thread Connection.