Sewer backups and backwater valves

The procedure

1. During a storm, use less water. When the sewer mains are full, anything you send down the drain has nowhere to go.
2. After a backup, stay out of the water. Sewage-contaminated water is a health hazard; keep children and pets away.
3. Protect yourself. Wear gloves, boots and eye protection for cleanup, and wash hands with clean water and soap afterward.
4. Throw out what can't be cleaned. Soaked carpet, cardboard and insulation usually go.
5. Plumber's step: a licensed plumber installs a backwater valve in the sewer lateral, usually in a pit with an access cover, under a permit.
6. Keep it working. A check-type valve can be held open by debris, so FEMA says it needs periodic cleaning. The valve is part of your lateral, so it is yours to maintain.

Why do shore houses get sewer backups in storms?

Storm surge and heavy rain fill the street sewers on low barrier islands. When the mains are at capacity, the lowest drain in the house, often a garage floor drain or a ground-floor shower, becomes the overflow.

Which kind of backwater valve?

FEMA describes check valves that close on their own, gate valves that are closed by hand and seal better, and dual valves that combine both for homes with repeated backups. A plumber can tell you which your lateral can take.

The numbers behind it

Questions owners ask

Does homeowners insurance cover sewer backup?

Often only with a specific endorsement. Check your policy.

Can I install a backwater valve myself?

It goes into the sewer line under a permit; this manual leaves it to a licensed plumber.

Why did sewage come up through the garage drain?

It is usually the lowest opening to the sewer, so it overflows first.