(1) The walls of every manhole installed on a sewer shall be—

a) constructed of brickwork not less than 200 millimetres thick, composed of bricks, complying with the requirements of C.A.S. No. A35, Burnt clay building bricks and blocks, set in cement mortar having a composition not inferior to three parts of sand to one part of cement by volume; or

b) of concrete construction of either—

i) a minimum thickness of 150 millimetres of cast-in-situ concrete; or

ii) a minimum thickness of 100 millimetres of pre-cast vibrated concrete; or

iii) a minimum thickness of 60 millimetres of pre-cast spun reinforced concrete tube.

(2) The base of every manhole shall be not less than 150 millimetres thick and shall be constructed of Grade 20 concrete.

(3) The invert and channel shall be properly formed with salt-glazed earthenware channels, or other approved material, the sides of the channel being raised up vertically to the level of the pipe soffit and benched therefrom at a slope of 1 in 6, steel-trowelled to a smooth finish.

(4) Single-seal or double-seal covers of cast iron complying with the requirements of S.A.B.S. 558, Cast iron surface boxes and manholes and inspection covers and frames, shall be used, and shall be –

a) raised 100millimetres above ground-level; or

b) installed in such manner and at such a greater height above ground-level as shall, in the opinion of the local authority, exclude surface-water and storm-water.

(5) Heavy-duty types of cast iron covers complying with the specification referred to in subsection (4), shall be used in areas subject to heavy vehicular traffic.

(6) The recesses of manhole-cover frames shall be filled with anti-friction grease, and the covers shall be set in the recesses so as to form gastight coverings.

(7) The minimum inside dimensions of manholes shall be 600 millimetres in length by 450 millimetres in width up to 1 metre deep, and 900 millimetres in length by 600 millimetres in width over 1 metre deep:

Provided that the local authority may permit the use of circular manholes of equivalent size, and may demand larger manholes than those specified in this section where conditions render such larger manholes necessary.

(8) Where required by the local authority, approved metal rungs for the purpose of access shall be built into the wall of every manhole exceeding 1,25 metres in depth.