Hannibal Board of Public Works plans a smoke test of the city’s sanitary sewer system this month.

The tests are performed periodically throughout the year to help identify where unauthorized water is entering the sanitary sewer system. BPW says the unauthorized water can cause an unnecessary load on the wastewater treatment plant and could potentially cause sanitary sewer overflows.

During the tests, smoke is forced into sewer lines where it helps identify broken manholes, cross connections and cracked mains. The smoke is non toxic and harmless.

BPW officials say they’ll put out door hangers in neighborhoods a few days before the test with additional instructions.