B2E Expansion Tank Calculator


System Size Table
Pipe Dia. (in) Run Length (ft) Volume (Gal)
Water Holding Devices Vol. (Gal)
Total System Vol. (Gal) 
System Parameters
Total System Volume (Gal)
Lower Temp. Value (°F)
Higher Temp. Value (°F)
Atmospheric Press. (psia)
Press. at Lower Temp. (psig)
Press. at Higher Temp. (psig)
Spec. Vol. of H2O at Low
Temp. (ft3/lb)*
Spec. Vol. of H2O at High
Temp. (ft3/lb)*
Linear Coeff. of Thermal Exp. (in/in*F)

Expansion Tank Size (Gal)
Closed Tank with Air/Water Interface
Open Tank with Air/Water Int.
Diaphragm Tank
  1. Enter all pipe sizes and lengths into the system size table, along with any water holding devices.
  2. Adjust the system parameters.
  3. Click on "Calculate" button to get the expansion tank size(s) for the gallon amount shown.

This application is provided "as-is". It is designed for a limited set of inputs, and should be used with care. B2E can't guarantee correctness of the results of this working demo. Please contact us if you need a more robust and complete solution.

* From table 3 in Chapter 6 of the 1997 ASHRAE Handbook - Fundamentals