AMTROL EX-15 15 Extrol Expansion Tank 2 gallon capacity (note: larger size is Amtrol EX-30) NOT for potable water, for use with closed hydronic heating and cooling systems Factory precharge: 12 psig Max. working pressure: 100 psig Max. operating temperature: 240 degrees F Watertight reservoir for expanded water Thick, heavy duty Butyl/EPDM diaphragm for long service life