(a) Pressure manifolds for pressure dosed gravity distribution shall meet the following minimum design and performance requirements:

• (1) uniform distribution of flow proportional to lateral length with a minimum of two feet of residual pressure head;

• (2) a pressure regulating valve incorporated in the supply line just prior to the pressure manifold to control pressure to the manifold;

• (3) a mechanism or device for measuring residual pressure head in the manifold;

• (4) a mechanism to stop flow to individual laterals;

• (5) a method to visually verify the flow to each individual lateral;

• (6) the feeder lines from the pressure manifold shall be of sufficient size and slope for effluent to flow by gravity to each lateral; and

• (7) the pressure manifold and appurtenances shall be designed and installed to be accessible for inspection, operation, maintenance, and monitoring.

(b) A distribution box or a drop box may be used to dissipate or distribute flow in a pressure dosed gravity dispersal system for parallel, serial, or sequential distribution. Such devices shall be watertight, corrosion resistant, constructed to withstand active and passive loads, and the volume of the device shall be such that when the dose volume is delivered, the box shall not overflow. The authorized agent shall approve the distribution device when it has been determined to be in accordance with Rule .0901(g)(9) through (11) of this Subchapter.

History Note: Authority G.S. 130A-335(e), (f), and (f1).