Extrol® expansion tanks accept expanded fluid in closed-loop hydronic systems to control pressure build-up, improve comfort and help reduce energy costs. Nearly seven decades after inventing the first diaphragm expansion tank, Amtrol® line-up now includes specialty models engineered for modern, high-efficiency systems. None of it would have been possible without Extrol® The One That Started It All™. Amtrol® EXTROL® Hydronic Expansion Tank, Vertical, Series: SX Series, 81 gal, 22 in Dia, 56 in Height, 100 psig, Acceptance Factor: 0.42, 34 gal Acceptance Capacity, 240 deg F, Heavy Duty Butyl/EPDM Diaphragm, Steel Shell, Urethane Topcoat, Domestic