GWS Pressure Tank Pre-charge settings

Changing transport regulations in some parts of the world have required that some pressure tanks be transported with lower than previous air pre-charge.


As was always the case, and especially now with pressure tanks being used in a greater variety of applications, it is necessary to correctly set the pre-charge air pressure to match the installation and to not void warranty.





  1. Pressure switch controlled pumps with differential pressure set at 140 kPa (20 psi), pre-charge the tank to 20 kPa (3 psi) below the cut in pressure.


  1. For pumps controlled by pressure switches with higher differential pressures, electronic controls or variable speed controls, pre-charge the tank to 65% of the maximum system pressure.


  1. Pressure tanks installed on mains pressure, pre-charge should be set at the mains pressure.


  1. For hot water expansion, pre-charge should be set at the mains pressure.