The City of Mountlake Terrace Public Works Department will begin smoke testing sewer lines today, Monday, Oct. 6.

Smoke testing is one of the most efficient and cost effective ways to locate and identify where unauthorized water is entering the public portion of the sewer system costing wastewater treatment facilities and taxpayers millions of dollars.

During smoke testing, crews blow air and smoke into the sewer system in the street and monitor where smoke escapes. The smoke fills the main line and any connections, and then goes to any leak and comes up to the ground surface revealing the source of the problem.

Smoke testing can help locate buildings that have downspout, cellar, yard or basement drains, and sump pumps, points of groundwater or surface water intrusion into the sewer, cross connections between sanitary sewers and storm drains, and defective sewer connections that could allow sewer gases into a building.

Residents may see smoke coming from manholes, downspouts, ground surfaces and storm drains for a brief period during the testing process. Smoke should not be entering homes because water in traps in sink and toilet drains should prevent it from getting in.

If you have a sink or toilet that is not used much, run some water down the drain or flush the toilet to refill the trap to prevent sewer gases from entering your home. If you are unsure of the source of the smoke in your home or yard, phone 911. The smoke testing program will take approximately one month. Public Works crews will notify residents when they are working in their immediate area.

For more information about the city’s smoke testing of sewer lines, please contact the Public Works Department at 425-670-8264.