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What are Storm Drains?

Mary McMahon
Updated: May 17, 2024

Storm drains are specialized drainage systems which are designed to handle an excess of water as a result of flooding or heavy rainfall. They are frequently found in major cities, especially in flood prone areas. A number of systems are used for the collection and ultimate discharge of water from these drains, and if there are drains of this kind in your area, it may be interesting for you to learn about how the water is processed before it is discharged.

When rainfall is heavy, the streets, parking lots, and other flat areas of a town can flood. In addition to the water falling directly on these surfaces, gutters also discharge large amounts of water into the street. The flooding can pose a hazard, which is why storm strains are installed. The storm drains are frequently located on either side of a street, at a low point in the roadway where water would naturally collect. Typically, a large grate covers the drain, which takes the form of a giant pipe.

In some parts of the world, storm drains are known as storm water drains or a surface water system. Water flows down the pipes and meets up with other pipes, creating an ever larger central pipe. In many areas, the storm drain system is kept entirely separate from the sewer system. The outlet for the pipe is found by a lake, ocean, or other major body of water. In other cases, these drains are connected with the sewer system, and the water from the drains is processed before it is disposed of.

When water from the storm drains flows into a body of water, it can potentially distribute flooding to locations downstream, in the case of a river. It also poses a major pollution risk, because spills in the streets will be carried through the unfiltered storm drain system. For this reason, people are warned to stay away from storm drains and outlets for their health. Many such drains also have signs above them which say “No dumping, drains to ocean” to remind people to protect their waterways by disposing of pollutants responsibly.

When a storm drain is linked with the sewage system and the water level is controllable, the processing offered by the sewage treatment plant is beneficial. However, if water levels start to rise beyond the capacity of the system, backups can cause the discharge of raw sewage into streets and waterways. For this reason, cities which chose to interconnect the storm drain and sewage systems must have protections in place to ensure the safety of the water supply.

About Mechanics is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a About Mechanics researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Discussion Comments
By anon69275 — On Mar 07, 2010

For number one. You will have to call the water municipal unit to get the correct size because it's their business and its a major safety hazard.

By anon34637 — On Jun 25, 2009

There is a very long leach pipe buried about one foot below the ground level in a patio. This leach pipe runs approx. 400 ft. in a straight line for 9 units. At least one section of the line is blocked. This is on private HOA property. What is the best way to solve the blockage problem to prevent backup on the patio during a big monsoon?

By anon16698 — On Aug 12, 2008

We have a large storm drain adjacent to our property. Currently it is not covered. How could I go about getting a cover for this?

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

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