Depth of pipe cover for drains

A drain should be laid either at a depth which will protect it from damage or with special protection over it (see paragraph 3.8). The maximum and minimum depths of cover for standard strength rigid pipes given in Table 3.3 should be used in conjunction with the classes of bedding given in Diagram 3.2. The depth of cover for flexible pipes used in conjunction with the bedding given in Diagram 3.3 should be – (a) a minimum of 600 mm under a vehicle area and 300 mm under other areas; and (b) a maximum of 10 m under all areas. The side cover for all types of pipe should be 150 mm or the diameter of the pipe, whichever is the greater. The depth of cover will normally depend on the levels of the connections to the drain, the gradient and the ground levels. If the depth is too little then imposed loads, agricultural activities, etc., or frost could cause damage. If the depth is too great then the weight of the backfilling could cause damage. A change of pipe material, bedding or backfilling may obviate the need for special protection against ground loads, and guidance is given in BS EN 752 and BS 8301.