24 CFR § 3280.603 - General requirements.
(a) Minimum requirements. Any plumbing system installed in a manufactured home shall conform, at least, with the provisions of this subpart.
(1) General. The plumbing system shall be of durable material, free from defective workmanship, and so designed and constructed as to give satisfactory service for a reasonable life expectancy.
(2) Conservation. Each water closet must not use more than 1.6 gallons of water per flush.
(3) Connection to drainage system. All plumbing, fixtures, drains, appurtenances, and appliances designed or used to receive or discharge liquid waste or sewage shall be connected to the manufactured home drainage system in a manner provided by this standard.
(4) Workmanship. All design, construction, and workmanship shall be in conformance with accepted engineering practices and shall be of such character as to secure the results sought to be obtained by this standard.
(5) Components. Plumbing materials, devices, fixtures, fittings, equipment, appliances, appurtenance, and accessories intended for use in or attached to a manufactured home shall conform to one of the applicable standards referenced in § 3280.604. Where an applicable standard is not referenced, or an alternative recognized standard is utilized, the plumbing component shall be listed by a nationally recognized testing laboratory, inspection agency or other qualified organization as suitable for the intended use.
(6) Prohibited fittings and practices.
(i) Drainage or vent piping shall not be drilled and tapped for the purpose of making connections.
(ii) Except as specifically provided elsewhere in this standard, vent pipes shall not be used as waste or drain pipes.
(iii) Fittings, connections, devices, or methods of installation that obstruct or retard the flow of sewage, or air in the drainage or venting systems in an amount greater than the normal frictional resistance to flow shall not be used unless their use is acceptable in this standard or their use is accepted as having a desirable and acceptable function of ultimate benefit to the proper and continued functioning of the plumbing system.
(v) Piping, fixtures or equipment shall be located so as not to interfere with the normal use or with the normal operation and use of windows, doors or other required facilities.
(vi) Galvanized pipe shall not be bent or welded.
(7) Alignment of fittings. All valves, pipes, and fittings shall be installed in correct relationship to the direction of flow.
(b) Protective requirements.
(1) Cutting structural members. Structural members shall not be unnecessarily or carelessly weakened by cutting or notching.
(2) Exposed piping. All piping, pipe threads, hangers, and support exposed to the weather, water, mud, and road hazard, and subject to damage therefrom, shall be painted, coated, wrapped, or otherwise protected from deterioration.
(4) Freezing. All piping and fixtures subject to freezing temperatures shall be insulated or protected to prevent freezing, under normal occupancy. The manufacturer shall provide:
(i) Written installation instructions for the method(s) required for compliance to this section;
(ii) A statement in the installation instructions required by § 3280.306(b), stating that if the heat tape or pipe heating cable is used, it must be listed for use with manufactured homes.
(5) All piping, except the fixture trap, shall be designed to allow drainage.
(6) Rodent resistance. All exterior openings around piping and equipment shall be sealed to resist the entrance of rodents.
(7) Piping and electrical wiring shall not pass through the same holes in walls, floors or roofs. Plastic piping shall not be exposed to heat in excess of manufacturers recommendation or radiation from heat producing appliances.