Potable Thermal Expansion Tank 1 Gallon, 3/4″ MNPT Connection, Compact Design fo
200 ℉ 200 ℉ 200 ℉ —. Potable Thermal Expansion Tank 1 Gallon, 3/4″ MNPT Connection, Compact Design for Water Heater, RV, Marine, Boat, Off-Grid Systems, Residential Plumbing & Solar Thermal. Food-grade Materials: The thermal expansion tank features a 3/4″ MNPT connection constructed of food-grade type 304 stainless steel.