CSLB C-36 Plumbing ContractorRough-in PlumbingMedium
A plumbing contractor is preparing to backfill a trench containing a newly installed underground water supply pipe. What is the minimum depth of cover required for underground potable water piping outside of a building, when not located under a slab or driveway?
- A24 inches
- B12 inches
- C6 inches
- D18 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 12 inches
The California Plumbing Code (CPC) requires a minimum of 12 inches of cover for underground potable water piping outside of a building, unless it is located under a slab or driveway where it may be less, or in areas subject to vehicular traffic which typically requires more cover.
Why the other options are wrong
- A. 24 inches is usually required for pipes under vehicular traffic or in colder climates for frost protection, but not the general minimum for all outdoor areas.
- C. 6 inches is generally insufficient cover for underground water lines and could lead to damage from frost or surface activities.
- D. 18 inches is more than the minimum required but could be used, though not the answer for 'minimum'.
Underground Water Pipe Cover
The minimum depth of soil or fill material required above an underground potable water pipe to protect it from damage, freezing, and surface loads.
- Protects from physical damage and frost.
- Varies based on location (e.g., under building, outdoors, under driveways).
- Specified by plumbing codes (e.g., CPC).
Memory trick: Water needs a Foot of dirt; Sewer needs a Foot and a Half.