RO Expansion Tank 4 Gallon &ndash; NSF Certified &ndash; Compact Reverse Osmosis Water Storage Pressure Tank by tankRO &ndash; with FREE Tank Ball Valve KEEP YOUR WATER HEALTHY - This tank is made from 100% food grade materials with a post cured diaphragm to ensure there are no chemicals in your water FREE TANK VALVE - Free tank valve included, designed for 1/4" quick connect setup CERTIFIED QUALITY - This tank is NSF certified and we include a 1 year warranty and every tank is tested at multiple stages to make sure it will last COUNT ON YOUR TANK - Heavy duty commercial construction with durable deep drawn steel domes and precision welded seams WHERE YOU NEED IT - Compact 15 x 12 x 12 size fits under most kitchen sinks WHEN YOU NEED IT - 4 gallon storage gives you water on-demand