Simple sanitary sewer system tool that helps you to calculate total infiltration to a sanitary sewer system. Infiltration is usually expressed in gallons per day per mile of sewer. With very careful construction, infiltration can be kept down to 5000 gal/(day.mi) [0.14 L/(km.s)] of pipe even when the groundwater level is above the pipe. With poor construction, porous soil, and high groundwater level, infiltration may amount to 100,000 gal/(day.mi) [2.7 L/(km.s)] or more. Sewers laid in dense soil where the groundwater level is below the sewer do not experience infiltration except during and immediately after a rainfall. Even then, the infiltration will be small amounts.
Formula:
Ti (gpd) = i
where,i is infiltration
sl is sewer system length