1959-HKRS30-8-49_Part03 — Page 1

Sub-soil

waler draias,

Size of drains.

Laying of drains and SEWEN.

(3) All pipes used in the construction of any drain or sewer shall-

(4) be of true bore;

(B) have smooth internal surfaces; and

(c) be impervious.

(4) Cast iron sewage pipes shall be protected against rust and corrosion by a suitable asphaltic coating.

(5) Earthenware, stone ware and concrete pipes shall—

(a) in the case of pipes with a diameter not exceeding six inches. have a thickness equal to not less than one-ninth of the diameter of the pipe; and

(b) in the case of pipes with a diameter exceeding six inches, bave a thickness equal to not less than one-twelfth of the diameter of the pipe.

45. Drains provided for the carriage of sub-soil water shall be constructed with clay field pipes or other suitable pipes and shall be laid to adequate falls.

46. All drains and sewers shall be of adequate, but not excessive, size for the purpose for which they are provided :

Provided that no covered drain shall have an internal diameter of less than four inches.

47. (1) All drains and sewers (except drains provided for the carriage of sub-soil water) and traps shall be firmly laid on a bed of concrete not less than four inches in thickness and at least six inches wider than the diameter of the pipe or trap, and shall be haunched with concrete so that the full width of the bed is carried up to the level of the horizontal diameter of the pipe and from that point splayed up on both sides of the pipe from the full width of the bed to meet the pipe barrel tangentially,

(2) All drains and sewers shall be supported along the full length of the barrels and not by the sockets.

(3) Where any drain or sewer is laid in soft and yielding ground- (a) adequate support shall be provided for such drain or sewer:

and

(6) save where the same are provided for the carriage of sub-soil water, the pipes shall be completely surrounded by at least four inches of concrete.

(4) Cast iron pipes above the ground may be carried on adequat piers or other sufficient supports, if such support is provided at each joint.

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48. Every drain or private sewer shall be laid with a minimum fall Fall of draina. from its highest inlet to its connexion with a public sewer or other outlet

in accordance with Table XII below.

TABLE XIL

Diameter of pipe

Fall

4* pipe

1 in 40

6" PIEC

1 in 70

9* pipe

1 in 100

1 in 150

12" pipe

49. (1) The junction of a single branch drain with another drain Junction of at an angle of not more than 45° in the direction of flow may be made drains, by means of a purpose-made Y junction.

(2) The junction of every other branch drain with another drain shall be made within a manhole, obliquely at an angle of not more than 60o in the direction of flow of such other drain. and shall be above the invert of such other drain.

50. (1) Every joint in a drain or sewer shall be made in a proper Joints. and efficient manner so as to render the drain or sewer watertight and capable of resisting a pressure of five-foot head of water, and no material forming any such joint shall project into the interior of any pipe in such manner as to cause any obstruction in the drain or sewer.

(2) The joints of cast iron socketed pipes shall be made with a gasket of hemp or yarn, and shall be properly caulked with metallic lead or other approved material.

(3) The joints of cast iron flanged pipes shall be made by bolting the flanges together securely with a suitable metallic or asbestos gasket.

(4) The joints of earthenware, stone ware or concrete pipes shall be made with a gasket of hemp or yarn, and cement mortar or other approved material.

51. (1) Every inlet at the upper extremity of every branch drain Inlets to of sewer, other than for a soil pipe or ventilating pipe, shall be properly drains, urapped by an efficient trap, which shall be so formed and fixed as to tuintain a water seal of not less than three inches.

(2) No inlet to any drain shall be made within a building except-

(a) an inlet which is a necessary part of the connexion of any

soil fitment or waste fitment;

() an inlet for the carriage of any trade effluent; or (c) where no other means of connexion is practicable.