100′
B
1 IN 40
2212
O<2′.6′′>[V
ORDINANCE No. 24 OF 1887.
Public Health.
At C, distant 60 feet A B is a drain 90 feet long, with an available fall of 3 feet, between A and B. from 1, there is a branch CD 40 feet long; D being at the same level as B.
F
1 IN 46.6
It is clear that an obstruction at A would be more easily removed than one at B, 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.
(.g. (2.)
\B
1 IN 30
-40
60′
90′
If the main-drain AB were given an uniform fall of 1 in 30, then would be 1 foot below B and D. Then CD would have a fall of 1 in 40 only. The proper course to pursue would be to give CD a fall of one in thirty, or 1′ 4″ in all. BC would then have a fall of 1′ 4″ in 30, or 1 in 223, and CA a fall of 1′ 8″ in 60 feet; or one in thirty-six.
Fall to drains and finish.
Change of direction.
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 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′ 0″ x 16″ to the surface or to a depth of five feet above the drain. Beyond this depth the manhole may be narrowed to 1′ 6″ x 16″). But such manhole 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.
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