In many older urban centres, downspout disconnection program require that residents retroactively disconnect downspouts. This is due to older sewer systems being undersized for the combined flow of sanitary waste and stormwater. New projects should consider remaining independent of the municipal sewer from the outset. This may involve employing series of small individual site LID technologies, or combining flow from a few sites to a shared facility.
The Ontario Building Code requires that:
"Where downspouts are provided and are not connected to a sewer, extensions shall be provided to carry rainwater away from the building in a manner that will prevent soil erosion."