Two examples of pump curves are presented in Figure 19. Select a pump that will provide sufficient head for the capacity needed. Avoid selecting too large a pump, with the GPM versus TDH far below the curve.
Large pumps are more expensive.
The required TDH for the GPM should be on or just below the pump curve, within the middle two-thirds of the curve, for most efficient operation. The purpose of the dosing system is to pump a predetermined volume of septic tank effluent from the dosing tank to the mound. The pump must be turned on when enough septic tank effluent collects in the dosing tank, and shut off when the effluent remaining in the tank reaches the solids storage level. The pump is usually controlled by float switches suspended in the tank, as shown in Figure 20. The settings for the switches are determined based on the dose volume and the size and geometry of the tank.