What Is a Storm Drain Backup and Can It Flood a Basement?

The storm drain system is designed to carry rainwater away from streets and properties. During heavy, sustained rain, this system can become completely overwhelmed by volume. If the main sewer line is blocked or at full capacity, water has nowhere to go but backward. It then seeks the lowest point, which is often a basement floor drain or a laundry connection.

Safety is the first priority. Avoid contact with the water, as it may contain contaminants from the street like oil, dirt, or chemicals. Turn off electricity to the basement at the main breaker if it is safe to do so from a dry location. Do not attempt to unclog the floor drain while water is present. You should contact local water damage pros to handle the water extraction and drying process safely and effectively.

While you cannot control the public sewer, you can take steps to protect your home. Installing a backwater valve on your main drain line is a key measure that can physically prevent sewer water from flowing back inside. Regularly inspect and clear your home's exterior drains and downspouts of leaves and debris. Ensure downspouts direct water at least six feet away from your foundation to reduce the burden on the local drainage system. Consider grading your yard so that it slopes away from the house, which helps direct surface water away from the foundation.