The N-12 Low Head Pipe specification covers pipe requirements, joint performance, fittings, field pipe & joint performance, material properties, and installation information.

The pipe requirements for the N-12 Low Head pipe indicate that the pipe shall have a smooth interior and annular exterior corrugations. 24”-60” (600 to 1500 mm). Pipe shall meet AASHTO M294, Type S or ASTM F2306 with the modifications listed herein. Manning’s “n” value for use in design shall be 0.012. Where low head applications sustain continuous pressure, the sustained pressure shall not exceed 5 psi and the surge pressure shall not exceed 10 psi.

The joint performance requires that the pipe is joined using a bell and spigot joint meeting the requirements of AASHTO M294 or ASTM F2306. The joint shall be watertight according to the requirements of ASTM D3212. Gaskets shall meet the requirements of ASTM F477. Gaskets shall be installed by the pipe manufacturer and covered with a removable, protective wrap to ensure the gaskets are free from debris. A joint lubricant available from the manufacturer shall be used on the gasket and bell during assembly. 12” - 60” (300 to 1500 mm) diameters shall have a reinforced bell with a polymer composite band installed by the manufacturer.

Fittings shall conform to AASHTO M294 or ASTM F2306. Bell & spigot connections shall utilize a welded or integral bell & inline, valley or saddle gaskets meeting the watertight joint performance requirements of ASTM D3212.

To assure watertightness, field performance verification may be accomplished by testing in accordance with ASTM F1417 or ASTM F2487

Material properties for pipe and fitting production shall be high-density polyethylene conforming with the minimum requirements of cell classification 435400C for the corrugated exterior profile, and 445464C, for the interior liner as defined and described in the latest version of ASTM D3350, except that carbon black content should not exceed 4%.

Installation shall be in accordance with ASTM D2321 and ADS recommended installation guidelines, with the exception that minimum cover in trafficked areas for 24”-48” (600 to 1200mm) diameters is one foot (0.3 m) and for 60” (1050-1500 mm) diameter the minimum cover shall be 2 ft. (0.6 m) in single run applications. For additional installation requirements refer to Technical Note 2.1.