1. Determine the relative elevation of 0.00 (generally 0.00 for the ground). 2. The elevation of the bottom of the water inlet pipe is the key to the elevation of the whole process. If the gravity flow only rises once in your design process, then calculate the elevation of your inlet pipe according to your final outlet elevation. For example, if the process is regulating tank+primary sedimentation tank+biochemical tank+sedimentation tank+disinfection tank, then the effluent of disinfection tank should be at least higher than the height of local river. Assuming that the ground elevation is 0.00 and the elevation of the nearby drainage river is-1.00, the effluent of your disinfection pool should be at least greater than-1.00. In this way, you can calculate the outlet elevation of the sedimentation tank, the outlet elevation of the biochemical tank, the outlet elevation of the primary sedimentation tank and the inlet elevation of the primary sedimentation tank in combination with the head loss of the disinfection tank. If your lift pump goes from the regulating tank to the primary sedimentation tank, the bottom elevation of the inlet pipe of your lift pump station should not be lower than the inlet elevation of the primary sedimentation tank. (Note that head loss is related to flow velocity, lift and elevation). According to the above, the bottom elevation of the intake pipe of your lifting pump station is finally obtained.