Expansion Tank Sizing Calculator

How do I size an expansion tank for a closed hydronic heating system?

First compute the water expansion volume from the change in water density between the cold-fill and hot operating temperatures, then apply the diaphragm-tank formula using the cold-fill (acceptance) and maximum (relief) pressures expressed in absolute terms. This calculator follows the ASHRAE Handbook (HVAC Systems and Equipment, Hydronic Heating) method with NIST water densities. Always round the result up to the next catalog tank size.

Related questions

• Why does the expansion tank depend on temperature?
• Does the expansion tank replace the relief valve?