(1) The total length of distribution pipe shall,
(a) not be less than 30 m when constructed as a shallow buried trench, or
(b) not be less than 40 m for any other absorption trench.
(2) Except as provided in Sentences (1), (3), and (4) every leaching bed constructed by means of absorption trenches shall have a total length of distribution pipe not less than the value determined by the formula,
L=QT/200
where,
L =total length of distribution pipe in metres,
Q =the total daily design sanitary sewage flow in litres, and
T =the design percolation time.
(3) Except as provided in Sentence (1), where a leaching bed receives effluent from a Level II, Level III or Level IV treatment unit as described in Table 8.6.2.2., the leaching bed may have a total length of distribution pipe not less than the value determined by the formula,
L=QT/300
where,
L =total length of distribution pipe in metres,
Q =the total daily design sanitary sewage flow in litres, and
T =the design percolation time.
(4) Except as provided in Sentence (1), where the leaching bed is constructed as a shallow buried trench, the total length of the distribution pipe shall not be less than the value determined by Table 8.7.3.1.