About Smoke Testing

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What's Next?

The City of San Luis Obispo Utilities Department will be performing sanitary sewer system smoke testing to detect I/I sources such as connected downspouts, driveway and yard drains, foundation drains, faulty connections, and storm sewer cross connections. The smoke testing consists of placing a high-capacity blower on top of a sanitary sewer manhole and forcing nontoxic, non-hazardous smoke down into the sewer system. The smoke travels through the sewer system and escapes through any connections, cracks, leaks, etc. along the way. This quickly reveals sources of inflow and infiltration that will help the city create a plan to reduce impacts to the sewer system, as well as work with property owners to make corrections.

What happens if a problem is identified?

  • Corrections within the public Right-of-Way are the responsibility of the City of San Luis Obispo and plans will be made to correct them as soon as possible.
  • Corrections on private systems are the responsibility of the property owner. The City will give a notice to the property owner explaining the deficiencies found, as well as, ways to correct the issues noted, with a timeline for correction completion.
  • Often corrections can be easy, such as disconnecting a downspout from the home's sanitary sewer lateral, or replacing a broken cleanout cap.

Important Information for Residents:

  • You will receive multiple notifications, including a door hanger notification 24 to 48 hours before smoke testing work begins in your area.
  • Areas that were identified as contributing the most I/I to the system are being tested first.
  • San Luis Obispo Police and Fire Departments are aware of the smoke testing areas and schedule.
  • You do not need to be home during the smoke testing fieldwork.
  • The smoke is nontoxic and will not affect plants or animals.

To prevent smoke from entering your building:

  • Make sure all drain traps and plumbing fixtures have water in them as soon as you receive the 24 to 48 hour smoke testing notice. 
  • Fill seldom-used drains (such as basement floor drains, garage sinks, etc.) with water by running the faucet for 30 to 60 seconds or filling with approximately three cups of water.

If smoke from the tests enters your building:

  • It will have a distinct odor, but is nontoxic and nonhazardous. Simply open windows and ventilate.
  • Please immediately notify the field technicians who are conducting the test in the area, as this could be an indication of a defect in your plumbing system. 
  • Possible defects could also allow sewer gases to enter your home, which are a potential health hazard. All property owners are responsible for correcting such defects by consulting a licensed plumber to ensure the proper connections are made.