What is Inflow and Infiltration?

Inflow and infiltration are surface water and groundwater that enter the sewage system.

Inflow is “clear” water from rainfall or snow melt that enters the sewage system through direct sources such as yard, roof and downspouts, cross-connections with storm drains, foundation drains that are illegally connected to the sewage system; improperly installed sump pumps (used by many homeowners to keep groundwater out of basements); and manhole covers.

Infiltration is “clear” water or groundwater that enters the sewage system through holes and cracks in defective maintenance hole structures, pipes, joints and connections.
 

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