=63. Regulators.=—Regulators are commonly used to divert the direction of flow of sewage in order to prevent the overcharging of a sewer or to regulate the flow to a treatment plant. Sewer regulators are of two types, those with moving parts and those without moving parts. An example of the moving part type is shown in Fig. 41. In this type as the sewage rises the float closes the gate to the inlet sewer, thus preventing the entrance of sewage under head from the larger sewer. There are many variations in the details of float controlled regulators, but the principle of operation is similar in all. These regulators can be adjusted to fix the maximum rate of flow to a relief channel or sewage treatment plant, or during times of storm to cut off the outlet to the dry weather channel. Another form of the moving part type is shown in Fig. 42.[43] It has been used extensively by the Milwaukee Sewerage Commission. In its operation the dry weather flow is diverted by the dam into the intercepter. It passes under the movable gate on its way to the treatment plant. As the flow increases the dam is overtopped and flood waters are discharged down the storm channel. The movable gate is hung on a pivot placed below center. As the water rises in the intercepter, the pressure against the upper portion of the gate becomes greater than that against the lower portion, and the gate closes. An opening is left at the bottom to allow an amount of sewage equal to the dry weather flow to escape beneath the gate to prevent clogging or sedimentation in the intercepter channel.
Objections to all moving part regulators are their need of attention and liability to become clogged.
FIG. 42.—Moving Part Regulator without Float. ]
FIG. 43.—Leaping Weir at Danville, Illinois. ]
Shadow of steel knife edge which forms the lip of the weir can be seen through the falling sewage. ]
The overflow weir and the leaping weir have no moving parts and are used for the regulation of the flow in sewers. A leaping weir is formed by a gap in the invert of a sewer through which the dry weather flow will fall and over which a portion or all of the storm flow will leap. One form of leaping weir is shown in Fig. 43. An overflow weir is formed by an opening in the side of a sewer high enough to permit the discharge of excess flow into a relief channel. A weir at San Francisco is shown in Fig. 44. A series of tests were run on leaping weirs and overflow weirs in the hydraulic laboratory of the University of Illinois. The type of leaping weir tested was formed by the smooth spigot end of a standard vitrified sewer pipe. The overflow weirs were formed by a steel knife edge in the side of the pipe parallel to its axis as shown in Fig. 45. Tests were made in 18–inch and 24–inch pipes on various slopes from 0.018 to 0.005, for both leaping weirs and overflow weirs. The overflow weirs were varied in length from 16 inches to 42 inches and were placed at various heights from 25 per cent to 50 per cent of the diameter above the invert of the sewer. As the result of the observations the following formulas were developed. For the leaping weir the expressions for the coordinates of the curve of the surfaces of the falling stream, are: