10-04-2017, 09:04 PM
rainwater diversion ppt download
Rainwater diversion system must include the following elements:
Pump Well
Rain Switch
Overflow Line
Pump Well
The point where separation of storm runoff from washwater takes place must consist of a pump well. During dry weather, the washwater that discharge into the well must be conveyed by means of a pump to discharge to the sanitary sewer. During rainfall periods, the pump must be automatically deactivated after 0.1 inch of rainfall, and all subsequent rainwater or stormwater that flows into the well must be diverted to the
storm drain.
Rain Switch
A device to detect rainfall similar to the detail shown on Figure 1 must be installed in an open area as close as possible to the pump well. The diversion system must contain electronically activated valves to divert the flow and an automatic timer. The rain switch must automatically deactivate the pump or close the valve whenever it detects 0.1 inch of rainfall so that no excess rainwater will be discharged to the sanitary sewer. The switch must not be reset while rain continues to fall. Once the rain has stopped, the switch is to be reset no earlier than two hours after the cessation of rain and the stormwater flows into the diversion system has become negligible. The rain collector must be installed in an area where it will remain directly exposed to rainfall. The collector and switch must also be located in an accessible area, as close as possible to the pump well and at a height not greater than six feet above the adjacent supporting surface (floor, deck or other permanent walkway). This will allow testing of the diversion system safely and without undue difficulty. A Y section with cap for the purpose of testing should only be installed when all other means are proven to be impractical.Overflow Line The diversion of rainwater or stormwater to the storm drain must be accomplished through the use of gravity overflow. The overflow line must be located in the pump well or slightly upstream and should be at the same elevation as the pumps effluent line. In the event that a gravity overflow is not feasible due to the surrounding grade of the property, the installation of a second pump to divert all rainwater may be allowed. This second pump must be automatically activated by the rain switch at the same time that the pump conveying washwater to the sanitary sewer is deactivated. The rating capacity of the secondary pump must be sufficient to prevent flooding.