St. Louis County, MO Building Safety: Plumbing Permits (2026)

P-126 of the Plumbing Code requires a permit before anyone performs plumbing, drainlaying, or process-drainage work, connects to a sewer, installs or removes a backflow prevention device, or ties a dedicated fire-suppression main into a potable water main, with narrow exceptions for minor repairs and for storm or sanitary sewers already maintained by the Metropolitan St. Louis Sewer District, a municipal street department, or the County highway department. P-130, which lets an owner-occupant of a detached single-family dwelling personally do minor work such as one bathroom, one water heater, or up to eight drainage fixture units.

200: a $47 permit processing fee applies to most work, and the minimum total permit fee is $94 with one inspection and no plan review, $124 with plan review, and $141 to $171 where two inspections are required; domestic water heater and dishwasher replacements carry a flat $47 total fee instead of the processing fee. An application is deemed abandoned 180 days after filing unless diligently pursued or a permit issued, though the Code Official may grant additional 90-day extensions for cause. This chapter reaches only unincorporated St. 020.