Sanitary Sewer Smoke Testing


Inflow/Infiltration Reduction Program

The City of San Luis Obispo Utilities Department will perform sewer smoke testing to detect inflow/infiltration sources of storm water entering the sewer system.

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Why Smoke Testing?

The goal is to prevent stormwater from entering the sanitary sewer system, in order to protect human health, private property, and our local environment.

What is Inflow/Infiltration?:

Inflow/Infiltration (I/I) is when stormwater or groundwater enters the wastewater collection system (also referred to as the sewer system). Inflow is stormwater directly entering the sewer system. Infiltration occurs underground when groundwater or rainwater enters the sewer pipes through cracks, holes, faulty connections and other openings.

Common Sources of Inflow/Infiltration:

  • Inflow sources include roof downspouts, yard and driveway drains, broken/missing sanitary cleanout caps, leaky manhole lids, sump pump connections, and storm sewer cross connections.
  • Infiltration sources include storm and groundwater flow from broken or defective sewer lateral, faulty lateral connections, roots, broken cleanouts.  
  • I/I can be on both private and public property, significant infiltration is attributed to private sewer laterals throughout the City. 

Reasons to reduce Inflow/Infiltration:

  • I/I increase’s the volume of wastewater in the City’s collection system up to five times the amount when peak wet weather events occur. This increases costs for treatment, causes sewage overflows and threatens human health, private property and the environment.
  • Overflows may also result in water quality violations, penalties and possible fines.