12VAC5-610-870. Gravity effluent mains.
A. Size. Mains transporting effluent by gravity shall have a minimum internal diameter of three inches.
B. Slope. Gravity mains shall have a slope of not less than six inches per 100 feet.
C. Materials. Gravity mains spanning disturbed soil shall meet the material specifications contained in 12VAC5-610-750. The mains shall meet the specifications until placed two feet in undisturbed soil or until termination in a structure. The remaining gravity mains shall have a minimum crush strength of 1500 pounds per foot and may be constructed of cast iron, plastic, vitrified clay or other material resistant to the corrosive action of sewage. All gravity mains shall be watertight, smooth bore, rigid conduits.
D. Appurtenances.
1. Joints. Gravity mains shall have joints of the compression type with the exception of plastic mains which may be welded sleeve or chemically fused.
2. Adapters. Joining of mains of different size and/or material shall be accomplished by use of a manufactured adapter specifically designed for that purpose.
3. Valves. Valves shall be constructed of materials resistant to the corrosive action of sewage. Valves placed below ground level shall be provided with a valve box and a suitable valve stem so that it may be operated from the ground surface.
E. Flow diversion devices. Flow diversion is a technique for increasing the useful life of an absorption area. Flow diversion provides for diversion of flow to two alternate equally sized absorption areas whose sum meets the area requirements in 12VAC5-610-950 B with a rest period of approximately one year for recovery of each absorption area. These devices shall meet the material requirements contained in paragraph D 3 of this section.
F. Construction. Construction standards for gravity effluent mains are the same as those for house sewers and are found in 12VAC5-610-770.
Statutory Authority
§§ 32.1-12 and 32.1-164 of the Code of Virginia.
Historical Notes
Derived from VR355-34-02 § 4.22, eff. February 5, 1986; amended, eff. May 11, 1988.