// CODE SNIPPET
1310.1 Piping Underground
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Underground gas piping shall be installed with approved clearance from any other underground structure to avoid contact therewith, to allow maintenance, and to protect against damage from proximity to other structures. In addition, underground plastic piping shall be installed with approved clearance or shall be insulated from any source of heat so as to prevent the heat from impairing the serviceability of the pipe. [NFPA 54:7.1.1]
Underground piping systems shall be installed with a minimum of 12 inches (305 mm) of cover. The minimum cover shall be increased to 18 inches (457 mm) if external damage to the pipe or tubing from external forces is likely to result. Where a minimum of 12 inches (305 mm) of cover cannot be provided, the pipe shall be installed in conduit or bridged (shielded). [NFPA 54:126.96.36.199]
The trench shall be graded so that the pipe has a firm, substantially continuous bearing on the bottom of the trench. [NFPA 54:188.8.131.52]
Where flooding of the trench is done to consolidate the backfill, care shall be exercised to see that the pipe is not floated from its firm bearing on the trench bottom. [NFPA 54:184.108.40.206]
Zinc coating (galvanizing) shall not be deemed adequate protection for underground gas piping. [NFPA 54:220.127.116.11]
Underground piping shall comply with one or more of the following unless approved technical justification is provided to demonstrate that protection is unnecessary:
- The piping shall be made of corrosion-resistant material that is suitable for the environment in which it will be installed.
- Pipe shall have a factory-applied, electrically insulating coating. Fittings and joints between sections of coated pipe shall be coated in accordance with the coating manufacturer's instructions.
- The piping shall have a cathodic protection system installed, and the system shall be maintained in accordance with Section 1310.1.3.3 or Section 1310.1.3.6. [NFPA 54:18.104.22.168]
Cathodic protection systems shall be monitored by testing and the results shall be documented. The test results shall demonstrate one of the following:
- A pipe-to-soil voltage of -0.85 volts or more negative is produced, with reference to a saturated copper-copper sulfate half cell.
- A pipe-to-soil voltage of —0.78 volts or more negative is produced, with reference to a saturated KCl calomel half cell.
- A pipe-to-soil voltage of —0.80 volts or more negative is produced, with reference to a silver-silver chloride half cell.
- Compliance with a method described in Appendix D of Title 49 of the Code of Federal Regulations, Part 192. [NFPA 54:22.214.171.124]
Sacrificial anodes shall be tested in accordance with the following:
- Upon installation of the cathodic protection system, except where prohibited by climatic conditions, in which case the testing shall be performed not later than 180 days after the installation of the system.
- 12 to 18 months after the initial test.
- Upon successful verification testing in accordance with Section 1310.1.3.4(1) and Section 1310.1.3.4(2), periodic follow-up testing shall be performed at intervals not to exceed 36 months. [NFPA 54:126.96.36.199]
Impressed current cathodic protection systems shall be inspected and tested in accordance with the following schedule:
- The impressed current rectifier voltage output shall be checked at intervals not exceeding two months.
- The pipe-to-soil voltage shall be tested at least annually. [NFPA 54:188.8.131.52]
Documentation of the results of the two most recent tests shall be retained. [NFPA 54:184.108.40.206]
Where dissimilar metals are joined underground, an insulating coupling or fitting shall be used. [NFPA 54:220.127.116.11]
Where the formation of hydrates or ice is known to occur, piping shall be protected against freezing. [NFPA 54:7.1.4]
Underground piping, where installed through the outer foundation or basement wall of a building shall be encased in a protective sleeve or protected by an approved device or method. The space between the gas piping and the sleeve and between the sleeve and the wall shall be sealed to prevent entry of gas and water. [NFPA 54:7.1.5]
Where gas piping is installed underground beneath buildings, the piping shall be either of the following:
The conduit shall extend into an accessible portion of the building and, at the point where the conduit terminates in the building, the space between the conduit and the gas piping shall be sealed to prevent the possible entrance of any gas leakage. Where the end sealing is of a type that retains the full pressure of the pipe, the conduit shall be designed for the same pressure as the pipe. The conduit shall extend at least 4 inches (102 mm) outside the building, be vented outdoors above finished ground level, and be installed so as to prevent the entrance of water and insects. [NFPA 54:18.104.22.168]
Where the conduit originates and terminates within the same building, the conduit shall originate and terminate in an accessible portion of the building and shall not be sealed. [NFPA 54:22.214.171.124]
Plastic piping shall be installed outdoors, underground only.
- Plastic piping shall be permitted to terminate aboveground where an anodeless riser is used.
- Plastic piping shall be permitted to terminate with a wall head adapter aboveground in buildings, including basements, where the plastic piping is inserted in a piping material permitted for use in buildings. [NFPA 54:126.96.36.199]
An electrically continuous corrosion-resistant tracer shall be buried with the plastic pipe to facilitate locating. The tracer shall be one of the following:
- A product specifically designed for that purpose.
- Insulated copper conductor not less than 14 AWG.
Where tracer wire is used, access shall be provided from aboveground or one end of the tracer wire or tape shall be brought aboveground at a building wall or riser. [NFPA 54:188.8.131.52 — 184.108.40.206.2]
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