### Building (Standards of Sanitary Fitments, Plumbing, Drainage Works and Latrines) Regulations 《建築物(衞生設備標準、水管裝置、排水工程及廁所)規例》

47A. Drains and sewers in gathering grounds to be watertight
(1) Every drain or sewer provided for the carriage of foul water from any building which lies within a gathering ground shall be watertight and shall—
(a) be laid in pipes of cast iron or other approved material and be of such design and construction as to be capable of resisting the pressure to which it is likely to be subjected;
(b) have any hatch box constructed on the drain or sewer so that the hatch box is capable of resisting the pressure to which it is likely to be subjected; and
(c) have every joint in the drain or sewer made in lead, or other approved material so as to render the drain or sewer capable of resisting the pressure to which the drain or sewer is likely to be subjected.
(2) Every joint in a drain or sewer referred to in paragraph (1) shall be made by bolting the flanges together securely with suitable metallic or asbestos gaskets or shall be of such other approved construction so as to render the drain or sewer capable of resisting the pressures to which the drain or sewer is likely to be subjected.
(3) Hatch boxes shall be provided to a drain or sewer referred to in paragraph (1)—
(a) at intervals not exceeding 30 m in the drain or sewer;
(b) at changes of gradient, if the Building Authority so requires; and
(c) at every change in direction in the drain or sewer:
Provided that no hatch box is required where the change in direction does not exceed 10o and is made by means of a purpose-made bend.(4) Notwithstanding paragraph (3), not more than one manhole shall be permitted in each drain or sewer.
(5) Every hatch box shall be constructed of cast iron or other approved material and shall have a hatch or door securely bolted at the top thereof.
(6) In this regulation—
gathering ground (集水區) has the same meaning as in the Waterworks Ordinance (Cap. 102);
hatch box (檢查箱) means a chamber of such a size and form as readily allows inspection and testing of the drain or sewer on which it is constructed and the clearance of obstructions from the drain or sewer.
(L.N. 361 of 1980)

48. Falls of drains
Every drain or private sewer shall be laid with a minimum fall from its highest inlet to its connexion with a public sewer or other outlet in accordance with Table 29.Table 29     Diameter of pipe  Fall    100 mm   1 in 40   150 mm  1 in 70   225 mm  1 in 100   300 mm   1 in 150  
(L.N. 294 of 1976; L.N. 191 of 2015)

### Building (Standards of Sanitary Fitments, Plumbing, Drainage Works and Latrines) Regulations 《建築物(衞生設備標準、水管裝置、排水工程及廁所)規例》

49. Junction of drains
(1) The junction of a single branch drain with another drain at an angle of not more than 45o in the direction of flow may be made 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. Joints
(1) Every joint in a drain or sewer shall be made in a proper and efficient manner so as to render the drain or sewer watertight and capable of resisting a pressure of a head of water of—
(a) 1.5 m; or (L.N. 294 of 1976)
(b) the vertical distance between the invert level of the pipe joint and the level of the top of the manhole immediately preceding the joint,
whichever is the greater, 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. (L.N. 361 of 1980) 
(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. Inlets to drains
(1) Subject to paragraph (2), every inlet to a drain or sewer shall be properly trapped by an efficient trap, which shall be so formed and fixed as to maintain a water seal of not less than 75 mm.
(2) Paragraph (1) shall not apply—
(a) to an inlet for a soil pipe or a ventilating pipe;
(b) to an inlet for the carriage of any trade effluent;
(c) where no other means of connexion is practicable; or
(d) to an inlet to a drain used solely for the conveyance of rain water from a roof.
(L.N. 361 of 1980)

52. Ventilation
(1) Every drain provided for the carriage of foul water shall be ventilated at its highest point by means of a ventilating pipe having an internal diameter of not less than 50 mm. (L.N. 294 of 1976)
(2) Every manhole in which a disconnecting trap is fixed shall be adequately ventilated.
(3) Branch drains shall be ventilated at their highest point, if the Building Authority so requires.

### Building (Standards of Sanitary Fitments, Plumbing, Drainage Works and Latrines) Regulations 《建築物(衞生設備標準、水管裝置、排水工程及廁所)規例》

53. No traps between ventilated points
No trap or other obstruction to the free circulation of air shall be placed between the ventilation openings at the lower and higher ends of any drain or sewer.

54. Drains and sewers under buildings, etc.
(1) All drains and sewers under a building shall be laid in straight lines and shall be laid with cast iron sewage pipes.
(2) Where any drain or sewer is laid through any building, or where any building is constructed over any drain or sewer, relieving arches or beams shall be provided to protect such drain or sewer and to prevent any load from the building being transmitted to such drain or sewer.

55. Manholes and cleaning eyes to be provided
(1) Manholes shall be provided—
(a) at every change in direction in any drain or sewer except where—
(i) the change in direction does not exceed 45°;
(ii) the internal radius of the bend is not less than 6 times the internal diameter of the drain or sewer; and
(iii) the change in direction is made by means of a purpose-made pipe; and
(b) at changes of gradient, if the Building Authority so requires.
(2) Manholes or cleaning eyes shall be provided at intervals not exceeding 60 m in every drain and sewer. (L.N. 294 of 1976)