Amtrol: ST Models: Therm-X-Trol Inline Thermal Expansion Tanks, 5-Year Warranty

Amtrol invented the thermal expansion tank to absorb expanded water in closed, hot water systems and protect the water heater. Since the beginning, we’ve kept the pressure on our competitors with features they just can’t match; like our patented Turbulator™, antimicrobial liner, patent-pending InSight™ service indicator cap and 50 PSIG precharge. When your water heater is on the line, we deliver.

Amtrol: ST Models: Therm-X-Trol Inline Thermal Expansion Tanks Features

Accepts expanded water as system temperature rises and returns hot water to system when demand occurs.
Required by most building codes and water heater warranties.
50 PSI factory precharge; the industry's highest.
InSight® Indicator Cap, Antimicrobial Liner™ and Turbulator™