Backwater Valves Explained: When Georgia Homes Need One

What a backwater valve does

FEMA's homeowner retrofitting guide describes the problem: flooding can overload sanitary sewers, and water can then move backward through sewer lines and out of toilets and drains (FEMA). A backwater valve lets wastewater leave the house normally but closes when the flow reverses. Gwinnett County's Department of Water Resources puts it the same way: when sewage backs up at the upstream manhole, the device closes and keeps it from entering the home (Gwinnett County).

The 2024 International Plumbing Code (IPC) places the valve in the building drain or in the horizontal branch that serves the protected fixtures (IPC Section 714.1). Gwinnett notes that valves are often on the sewer lateral outside but may be inside the home.

Don't confuse it with the backflow prevention assembly a water utility may require on a drinking-water line. Atlanta's Department of Watershed Management describes that device as a pair of check valves on the water service line that keeps contaminants out of the public water supply (Atlanta DWM). A sewer backwater valve protects your house from the sewer; a water backflow assembly protects the water system from your house.

When Georgia's plumbing code requires one

Georgia has adopted the 2024 IPC with Georgia amendments, and those amendments leave the backwater valve section as written (Georgia DCA). The Georgia Department of Community Affairs (DCA) gives January 1, 2027 as the effective date in its most recent announcement (December 2025), while an earlier DCA memo said January 1, 2026 (announcement; memo), so ask your city or county building department which edition it enforces. Section 714 reads the same in the 2018, 2021 and 2024 editions of the IPC. Section 714.1 says that where fixtures are installed on a floor whose finished floor elevation is below the manhole cover of the next upstream manhole in the public sewer, those fixtures must be protected by a backwater valve. Fixtures on floors above that level must not drain through the valve, although existing buildings are exempt from that part (IPC).

Gwinnett County states it plainly: if your lowest fixture, such as a basement toilet or sink, sits below the next upstream manhole, Georgia's plumbing code requires a sanitary backwater valve between your home and the public sewer. The county adds that the rule isn't new, that owners of older homes may want to check whether they have one, and that maintaining the valve is the homeowner's responsibility. It also says that if the code requires a valve and there isn't one, the county won't be responsible for damage from a backup in its main (Gwinnett County).

That's one utility's policy. Other Georgia sewer providers may word theirs differently, so check your provider's website or bill. For coverage questions, see sewer backup insurance in Georgia.

How to tell whether the rule applies to your house

1. Find the lowest floor with plumbing fixtures, such as a basement bathroom or laundry.
2. Identify the next manhole upstream on the public sewer from where your line connects. Your sewer provider may be able to tell you which one that is.
3. Compare that floor's finished elevation with the manhole cover's elevation. A licensed plumber can measure both. If the floor is lower, the code calls for a valve on the lines serving those fixtures.

Types of backwater valves

FEMA's guide describes three kinds (FEMA):

• Check (flap) valves work on their own: a flap lets wastewater out and closes when flow reverses. Debris can hold them open, so they need regular inspection and cleaning.
• Gate valves are closed by hand. They seal better and are unlikely to be jammed open, but they cost more and only help if someone closes them in time.
• Dual valves combine a check valve and a gate valve. They cost the most and are mainly for homes with repeated backups.

FEMA notes that gate and dual valves are usually installed outside the house in a valve pit. Whatever the type, the IPC requires the valve to meet one of three product standards, ASME A112.14.1, CSA B181.1 or CSA B181.2, so ask the installer which one yours meets (IPC Section 714.2).

Maintenance and access

The IPC requires backwater valves to be installed so the working parts can be reached (IPC Section 714.3). A FEMA presentation on basement flooding adds that valves can jam open with debris and that every type should have access for cleaning and repair (FEMA presentation).

Practical habits help:

• Know where the valve's access cover is, and keep it clear of mulch, pavers and stored boxes.
• Follow the manufacturer's maintenance instructions, and have a plumber check the valve periodically and after any backup.
• While the valve is closed during a backup, water you run in the fixtures it protects has nowhere to go, so hold off on using them.
• If you don't know whether you have a valve, a plumber's inspection or a sewer camera can tell you.

Leave opening and servicing the valve to a plumber, especially during or right after a backup.

Alternatives and add-ons

A backwater valve isn't the only way to protect low fixtures. FEMA's basement flooding presentation describes others (FEMA presentation):

• An overhead sewer. Everything collected below grade in the basement is pumped up to a sewer connection near the basement ceiling, so the basement has no direct connection to the sewer. FEMA calls this very effective but costly because of the plumbing changes.
• Standpipes and floor-drain plugs. These lower-cost measures cover floor drains. FEMA says a standpipe may suit basements where past backups were only a few inches deep, that float-type plugs can be blocked open by small debris, and that plugs shouldn't be used where flooding may exceed 3 to 4 inches, because a plug in severe flooding can lead to ruptured pipes or a cracked floor.

When fixtures are pumped, the code covers that equipment too: the discharge line from a sewage pump or ejector needs a check valve and a full-open valve, both accessible (IPC Section 712).

Next step

Find out how your lowest plumbed floor compares with the next upstream manhole on the public sewer. If it's lower and you have no valve, ask a licensed plumber about installing one; FEMA notes that backflow valves and other plumbing changes are usually regulated by state and local codes, so ask about the permit before work starts (FEMA). How to hire a drain cleaning company in Georgia explains how to check a contractor. This guide is general information, not legal or insurance advice; your local building department, your sewer provider, a licensed plumber and your insurer can tell you what applies to your home.