CSLB C-36 Plumbing ContractorRough-in PlumbingMedium
A plumbing inspector is reviewing a rough-in installation for a new gas piping system in a residential garage. The inspector notes that a section of 1-inch diameter black iron gas pipe is unsupported horizontally for a length of 12 feet. According to the UPC, what is the maximum unsupported horizontal length permitted for this pipe size?
- A12 feet
- B8 feet
- C10 feet
- D14 feet
Show answer & explanationAnswer & explanation
Correct answer: C. 10 feet
The Uniform Plumbing Code (UPC) specifies maximum unsupported horizontal lengths for gas piping to prevent sagging and ensure system integrity. For 1-inch nominal diameter black iron pipe, the maximum unsupported length is 10 feet.
Why the other options are wrong
- A. 12 feet exceeds the maximum permitted unsupported length for 1-inch gas pipe, making the observed installation non-compliant.
- B. This is the maximum unsupported length for 3/4-inch gas pipe, not 1-inch.
- D. This length is generally too long and not permitted for 1-inch gas pipe.
Gas Pipe Horizontal Support
The maximum allowable distance between supports for horizontal gas piping to prevent sagging, maintain proper slope, and ensure structural stability of the system.
- Prevents pipe sagging and stress on joints.
- Support intervals vary by pipe material and diameter.
- Ensures long-term system integrity.
Memory trick: Gas pipes need 'Steady Stands' to stay strong.