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City of San Mateo Municipal Code.


(a) A building sewer serving fixture(s) which have flood level rim(s) less than 12 inches above the elevation of the next upstream manhole and/or flushing inlet cover at the public sewer system serving such drainage piping shall be protected from backflow of sewage.

(b) Protection from backflow shall be by means of a backwater valve approved by the building official supplemented by an approved sewer relief valve installed with its outlet at least six inches below the flood level rim of the lowest installed drainage unit fixture. Fixtures above that elevation shall not discharge through the backwater valve without prior written approval of the building official. As an alternative, the system may be protected by installation of an approved sewage ejector or pump.

(c) A property owner shall ensure that backwater protection is installed and fully operable in the building sewer or sewers serving the property owner's real property whenever an inadequate height differential situation exists on the property.

(d) Whenever any drainage fixture unit is to be added to real property, the property owner shall obtain and file with the building official at the time of application for a building permit for the fixture unit a written certification by a licensed professional determining whether an inadequate height differential situation exists on the real property. If such a situation exists, the property owner shall provide the backwater protection described in this section, or permanently remove the drainage unit fixture or fixtures that have an inadequate height differential before completion of installation of the additional drainage unit fixture.

(e) Instead of providing certification pursuant to subsection (d) as applicable, a property owner may file a certification from a licensed professional demonstrating that backwater protection as approved by the building official has been installed on the property's sewage drainage system and is fully operable. This certification is subject to inspection confirmation by the City.

(f) The property owner is responsible for ensuring that backwater protection is properly maintained and functioning at all times. Backwater protection is subject to inspection by the City at any reasonable time, and failure to properly install and maintain this protection may result in suspension of sewer service.