Work out sewage generation for township instantly with clear inputs, formula shown and shareable results.
Sewage flow is a fraction of water supplied, typically eighty percent, because the rest is consumed, evaporated or used outdoors. Groundwater infiltration and stormwater inflow are added on top. Sewers are sized on peak flow while treatment plants are sized on average flow with a margin, because treatment processes need steady loading.
Average sewage flow
MLD = water supplied x return factor x (1 + infiltration allowance)
Peak flow
Peak = average x peak factor, typically 2.25 to 3.0
Preliminary estimate only. Sewerage design must follow the applicable manual on sewerage and sewage treatment.
MLD = water supplied x return factor x (1 + infiltration allowance). Sewage flow is a fraction of water supplied, typically eighty percent, because the rest is consumed, evaporated or used outdoors.
Sewers must physically carry the peak or they surcharge. Treatment plants use balancing and equalisation, so they are sized on average load with margin rather than the instantaneous peak.
This calculator takes 4 inputs: Water supplied, Return factor to sewer, Infiltration and inflow allowance, Peak flow factor. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.