Tier1 Comparable RO-132-W14 3.2 Gallon Reverse Osmosis System Bladder Tank 3.2 Gallon Reverse Osmosis System Tank for Reverse Osmosis Systems. The RO Tank has a 1/4 NPT stainless steel connector at the top of the tank There is a side mounted air valve for re-pressurizing the tank when needed. This RO tank has been tested and certified by NSF International under NSF/ANSI Standard 58 for material 100% TIER1 NO WORRIES GUARANTEE - We stand behind the quality of filtration and overall performance of our Tier1 filters!