Storm drains

A storm drain, storm sewer (U.S. and Canada), surface water drain/sewer (United Kingdom), or stormwater drain (Australia and New Zealand) is designed to drain excess rain and ground water from impervious surfaces such as paved streets, car parks, parking lots, footpaths, sidewalks, and roofs. Storm drains vary in design from small residential dry wells to large municipal systems.

Drains are fed by street gutters on most motorways, freeways and other busy roads, as well as towns in areas which experience heavy rainfall, flooding and coastal towns which experience regular storms. Even the gutters from houses and buildings can be connected to the storm drain. Many storm drainage systems are designed as gravity sewers draining untreated storm water into rivers or streams. As a result, it is not acceptable to pour certain types of chemicals into the drains.

Storm drains are often unable to manage the quantity of rain that falls during heavy rains and/or storms. When storm drains are inundated, basement and street flooding can occur. In many areas, detention tanks are required to be installed inside a property and are used to temporarily hold rainwater runoff during heavy rains and restrict the outlet flow to the public sewer. This lessens the risk of the public sewer being overburdened during heavy rain. Some storm drains lead to a mixing of stormwater (rainwater) with sewage, either intentionally – in the case of combined sewers – or unintentionally.

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