I need to install two AARA -type devices (Automatic Air Regulation Anti-Waterhammer) to prevent against water hammer in a wastewater pumping station. The manufacturer suggests two tanks of 265USg each. The supplier has modelled the process by which the tanks will empty completely as air is introduced into the pipes during pressure transients. I know that this situation is not ideal. However, could we still allow a percentage of air volume in the pipe? How can I improve the situation? Should I increase the size of the waterhammer tanks? Any advice would be greatly appreciated.