Roof Drains: Stormwater Compliance Photo Comparison
Roof Drains Connected to Sanitary Sewer
If stormwater is likely to contain pollutants from coming in contact with the roof surface, it may be preferred to connect the roof drain to the sanitary sewer (not the storm sewer) or route to on-site pretreatment.
This is an example of a downspout discharge into a vegetated area. This system minimizes the volume of stormwater discharged into the storm drain system. If the roof is not expected to be contaminated from vents or some other industrial material, disconnecting roof drains is acceptable.
Roof drains discharging stormwater into an alley
Roof drains water flow should be directed to a vegetate area or basin to minimize the amount of water leaving the property. Alternatively, the drains could be directly connected to a cistern or other type of collection system so that the water can be later used for irrigation, etc. This would minimize localized flooding and volume of stormwater being discharged to sewer systems.
Photo courtesy of Tetra Tech, Inc.