T-12 Amtrol THERM-X-SPAN Expansion Tank, 4.4 Gallon The Amtrol THERM-X-SPAN T-12 Expansion Tank has a steel shell, plastic liner, and rubber diaphragm with a brass system connection. The maximum operating temperature is 200ºF and the maximum working pressure is 150 PSIG. Unit comes with a 40 PSIG factory precharge. Tank Volume (Gallons) - 4.4Max. Accept Factor - 0.73System Connection (Inches) - 3/4Height (Inches) - 15Diameter (Inches) - 11Shipping Weight (lbs.) - 9Temperature = 200°F. Maximum Working Pressure = 150 PSIGFactory Precharge = 40 PSIG