Sewer backup can occur not only when the municipal sanitary sewer system surcharges, but also when the municipal storm sewer system surcharges. A surcharging storm sewer can force water back into home storm sewer lateral connections. This water can then exfiltrate from (or be forced out of) storm sewer laterals. If the storm sewer lateral and the sanitary sewer lateral are close together, water that has exfiltrated from the storm sewer lateral can enter the sanitary sewer lateral and cause sewer backup in the home.

The storm sewer lateral should be severed as close to the municipal storm sewer as possible. This will reduce the chances that water will exfiltrate from the storm sewer lateral into the sanitary sewer lateral, thereby reducing the risk of sewer backup.

In some homes, weeping tiles may also be connected to the storm sewer lateral. If the weeping tiles are connected to the storm sewer lateral, a sump-pit and sump-pump should be installed to direct foundation drainage to the lot’s surface to allow for proper foundation drainage after the storm sewer lateral is severed (see Option 14).

High amounts of exfiltration from storm laterals into sanitary laterals can create significant excess flows of water in sanitary sewer systems. These excess flows can increase the risk of sewer backup for everyone in a neighbourhood. If a large group of homeowners sever storm sewer laterals that are subject to exfiltration, sewer backup risk can be reduced for everyone in the neighbourhood.

You will need permits from your municipal government and the assistance of professionals to sever your storm sewer lateral. Talk to your municipal government about this option before you consider severing your storm sewer lateral.