ORDINANCE No. 13 of 1901.
Public Health.
15. Whenever a reduction of fall (below the standard grade 1 in 30) is necessary or permissible, it shall, wherever practicable, be made in the portion of the drain nearest to the outlet, rather than in the part nearest to the inlet, and in the main trunk of the drain rather than in the branches.
NOTE. The available fall in a house-drain, 100 feet long, is 3 feet 4 inches by one in forty. It will be better to make the first sixty feet from the inlet, with a fall of 1 in 30; and the remaining length of 40 feet with a fall of 1 in 60, than give a uniform fall throughout.
100
BIN 40
It is clear that an obstruction at i would be more easily removed than one at f, in the pipe of uniform gradient, because it would have a greater head of water behind it; and in flowing from the inlet to it, the stream will have attained a certain momentum, tending to carry it on, through the flatter part of the pipe. e.g. (2)
AB is a drain 80 feet long, with an available fall of 3 feet, between A and B. At G, distant 50 feet from A, there is a branch G D 30 feet long: D being at the same level as B.
D
06
09
would be 1 foot below G and D. Then a fall of one in sixty, or 1 in 60, would be to give ...
If the main drain AB were given a uniform fall of 1 in 30, then G D would have a fall of 1 in 40 only. The proper course to pursue would thus be to make the fall 1 in 30 for the first 50 feet and 1 in 60 for the remaining 30 feet.
ORDINANCE No. 13 of 1901.
Public Health.
16. Whenever the gradient of any portion of a drain is less than one in thirty, the Sanitary Board may in its discretion require an automatic flush tank or any other suitable contrivance for attaining an effective flush to be used.
17. All changes of direction in house-drains shall be made by means of properly curved pipes or by half channels in manholes and between the points at which any change of direction occurs, all house-drains shall be laid in straight lines and regular grades from point to point.
NOTE. (Inasmuch as changes of direction are the points at which obstructions most frequently occur, and for the purpose of removing obstructions generally, house holders will do well to provide, at each change of direction, a manhole, giving access to the drain. For this purpose the manhole should be made 3 feet by 1 foot in area to the surface or to a depth of five feet above the drain. Beyond this depth the manhole may be narrowed to 1 foot 6 inches by 1 foot 6 inches, But such manholes should not be found in cook-houses or in places where they may be opened and used as receptacles for the disposal of solid rubbish.)
18. No drain shall be so constructed as to pass under any building except when any other mode of construction is impracticable. Any drain passing under a building shall (unless the written permission of the Sanitary Board has first been obtained to lay it otherwise) be laid in one straight line for the whole distance beneath such building, and shall be imbedded and incased throughout its entire length in four inches of good concrete.
Whenever a drain traverses soft or yielding ground, or where water may make its appearance in the trench, the drain shall be surrounded throughout its entire length with four inches of good concrete.
The stones composing the matrix of the concrete in both cases shall be of a size to pass through a half-inch ring.
19. No drain shall be constructed in such manner as to allow any inlet to such drain to be placed inside any building.
20. The aggregate area of the openings in any grating fixed on inlets to waste-pipes from baths or sinks shall not be less than four square inches and the waste-pipe shall not have a less internal diameter than 1.5 inches.
NOTE. The object of this is to secure an efficient flush.
21. Traps or galleys for the removal of rain-water shall be provided with gratings having the nett area of the openings not less than twice the area of the trap or pipe. Such gratings shall be sunk to a depth of at least one inch below the surrounding pavement, with a slope round them equal to half the width of the grating.
NOTE. It is not sufficient to provide pipes of ample diameter; there must be openings of sufficient size to admit the rain to them.
22. Traps at the inlets to drains shall be placed so that the water-level in them is not less than one foot below the ground, and such traps shall be placed as low down as the level of the house-drain or branch will permit of; provided that the depth be not more than two feet.
23. Traps shall have not less than two inches of water seal and shall be securely fixed to the drain. All stoneware traps shall be surrounded with a thickness of four inches of lime concrete.
24. No person shall construct or fix in connection with any drain or waste-pipe the form of trap of the kind known as the Bell-trap or any trap of the kind known as the D trap, and all traps connected with any private drains shall be properly set in cement mortar to the satisfaction of the Board.
NOTE. Bell-traps and D traps from their form give rise to deposit of filth difficult to remove by flushing.
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