Why Does My Sewer Back up When It Rains Hard?

When it rains hard, stormwater often enters the same sewer pipes that carry your household wastewater. In many older systems, these are combined sewers. During a heavy downpour, the volume of water can exceed the pipe's capacity, creating pressure that pushes sewage back up through your toilets, sinks, and floor drains.

Another common cause is a blockage in your own sewer lateral, the pipe that connects your home to the main sewer line. Tree roots, grease buildup, or a collapsed pipe can restrict flow, so even moderate rain can cause a backup. If your home has a sump pump, a power outage or pump failure can also lead to water rising in the basement.

Prevention starts with what you put down your drains. Avoid pouring grease, oil, or coffee grounds down the sink. Use a strainer in the shower and kitchen sink to catch hair and food particles. Flush only toilet paper, not wipes or other items, since these can clump and cause blockages.

Have a plumber inspect your sewer lateral periodically, especially if you have large trees near your property line. Root intrusion is a common issue in older neighborhoods. Consider installing a backwater valve on your main sewer line; this device prevents sewage from flowing backward into your home during heavy rain.

Sewage backups create a health hazard and can cause significant damage to drywall, flooring, and personal belongings. The pros are equipped to handle the cleanup safely. They use industrial fans and dehumidifiers to dry out the space, and they can remove and dispose of contaminated materials.

The pros can also inspect for hidden moisture that might lead to mold growth. If the backup has soaked your carpets or drywall, they may need to remove those materials. You can request a water damage inspection to assess the extent of the damage. For severe flooding, flood damage cleanup services are available.