At AboutMechanics, we're committed to delivering accurate, trustworthy information. Our expert-authored content is rigorously fact-checked and sourced from credible authorities. Discover how we uphold the highest standards in providing you with reliable knowledge.

What is a Backwater Valve?

A backwater valve is a crucial plumbing component that prevents sewage from flowing back into your home during heavy rainfalls or blockages. It acts as a one-way gate, safeguarding your living space from the unpleasant and hazardous effects of sewer backup. Wondering how it can protect your home and peace of mind? Let's explore its importance and functionality together.
B. Turner
B. Turner

A backwater valve is a plumbing component used to prevent sewage from backing up into a home or business. Many properties naturally prevent sewage backups due to their plumbing design or location. For homes with plumbing system limitations, or those located below the elevation of manholes on nearby streets, a backwater valve can offer tremendous benefits. If the public sewer system becomes backed up, these valves prevent sewage waste from entering the home through drains and plumbing fixtures. While backwater valves are optional in many locations, some building codes may require these valves for all new construction.

Under normal conditions, the backwater valve allows sewage and waste to leave the home unchecked. If a backup occurs and sewage begins to flow back towards the home, the valve is automatically activated to stop sewage from entering the home. When the valve is closed, occupants of the home are unable to use toilets, sinks or other fixtures within the building. Once the blockage clears and the valve reopens, plumbing fixtures can once again be used as needed.


Buyers can choose from three basic backwater valve designs, depending on budget and local codes. A check valve is the most economical, and consists of a simple ball or flap that closes automatically when sewage attempts to re-enter the home. These valves tend to require the most maintenance, and are the most prone to failure. Gate valves are more reliable, but are more expensive than basic check valves. They also require some manual intervention to close off and reopen the sewer lines after a blockage.

Combination backwater valves are the most expensive, but also the least likely to malfunction. They feature an air-filled chamber and gate that senses a backup and shuts off the line automatically. These valves also reopen the line once the blockage is cleared, and feature an alarm system to alert homeowners when the valve is opened or closed.

A properly-installed backwater valve offers obvious advantages to homeowners. These valves prevent the mess and expense of a sewage backup into the home, and help minimize the risk of unsanitary conditions. At the same time, buyers should be aware that these valves require professional installation, and often require a permit from the city or county government. It is also critical to choose the right valve based on the particular demands of each project or location. All backwater valves also require routine maintenance to ensure they will function as intended during a backup.

You might also Like

Discuss this Article

Post your comments
Forgot password?
    • Worker