• Strongest tank design featuring deep drawn steel and multi-dome construction Thickest diaphragm - heavy-duty butyl/EPDM Projection welded air stem to help eliminate leaks Patented InSight® service indicator cap Free-standing models available in 14 through 86 gal Combination packages include an air purger (1 in model 443 or 1-1/4 in model 444) and an air vent (model 700-C)

The one that started it All™. 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® lineup 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™.