iSpring T32M 4 Gallon Residential Pre-Pressurized Water Storage Tank for Reverse Osmosis (RO) Systems 4 Gallon Metal Pressurized Tank with up to 3.2 GallonHolding Capacity Stainless Steel 1/4" NPT Valve Thread Made from FDA listed, food grade material (Tested by independent third-party to meet NSF/ANSI Standard) Discharges effectively in both vertical and horizontal position Pre-pressurized between 7-10 psi for common use