Drainage, Waste & VentQuestion 137 of 360
Fixtures with flood-level rims located below the elevation of the next upstream manhole cover must be protected from sewer backflow by…
a.An approved backwater valve
b.A deeper trap seal
c.An air-admittance valve
d.A larger vent
Explanation
Fixtures whose flood-level rims are below the next upstream manhole cover can flood when the public sewer surcharges, so they must discharge through an approved backwater valve. Fixtures above that elevation must not drain through the backwater valve, so they still drain by gravity if the valve closes. This protects low fixtures without impeding normal flow from higher ones.
Law Reference: 2022 California Plumbing Code (CPC) §710.1Practice all 360 questions free — no signup required.
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