Smoke Testing & Dye Testing
Low-cost field methods for spotting illegal connections and defective service laterals.
Smoke testing pushes non-toxic smoke through a sewer segment under slight pressure; smoke emerging from a roof vent, foundation drain, or yard indicates a direct connection needing follow-up.
Dye testing (flushing colored dye down a specific fixture or downspout and watching for it in the sewer) confirms a specific suspected cross-connection more precisely than smoke testing alone.
Both methods require advance public notification, since unexpected smoke or dye appearing at a resident's property without warning generates avoidable complaint calls.
Smoke testing works best in dry weather with groundwater levels low, since a system already saturated from infiltration can mask smoke escape routes that would otherwise be obvious.
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