How Sewer Backwater Valves Prevent Basement Sewage Cleanup & Flood Situations

Featured, Opinion & Expertise
September 20, 2022

by David Balkan

Sewer backwater valve and pipe fittings on the ground.

Sewage backup remains a significant challenge to New York homeowners whenever there are sudden downpours. Indeed, on September 13, 2022, New Yorkers once more experienced torrential rainstorms and flooding where city sewers were surcharged and discharged into numerous people’s basements, leading to costly basement sewage cleanup demands. Whenever there’s a sudden downpour, you risk having a water backup issue in your basement.  It’s terrible enough having clean rainwater back up in your basement, but imagine foul sewage backing up into your basement, spoiling everything it touches. However, in most cases, installing a sewer backwater valve may stop this. 

A sewer valve will eliminate the need for basement sewage cleanup services and save you on all the costs and hassle.

The Cost of Sewage Backup & Basement Sewage Cleanup

The city puts in great effort to keep the main sewer systems clear and functional. However, backups can still occur. Sewage backups might occur if your lowest drain is 24″ or less above the closest upstream manhole. When a city sewer surcharges, even perfectly sound and functional house sewers can flood basements. That is because during a torrential rainstorm the water level in a public sewer can riser many feet above its normal flow level.


If you don’t have a sewer backflow valve fitted, raw sewage can back up into your basement, tubs, sinks, and toilets. Some residences experience this regularly during heavy rains. The damage not only offers serious health risks but is also difficult and expensive to clean up and fix. However, a mainline backwater valve can come to your rescue.

What is a Sewer Backwater Valve?

A sewer backwater valve, also known as a backflow or sewer backup valve, is a valve installed on a sewer line to allow water or sewage to flow in one direction—out of your home. Every time there is a sudden heavy downpour, the city sewer systems may become overloaded and allow sewage or water to flow back towards your property. If you have a sewer backwater valve installed, sewage will not be able to flow back into your home in the event of a sewer system backup.

Some local authorities mandate backwater valves, while others only recommend them. Professional plumbers can install them into newly built homes or retrofit them into older ones.

sewer backwater valves

Naturally, installing during initial construction is far less expensive. When retrofitting, some concrete must be removed to reach the main sewer line. Certain municipalities offer subsidies to help with the cost of installing backwater valves.

There is a higher risk of sewage backup if your property has a basement or the ground floor is lower than a foot above street level. The National Plumbing Code stipulates that backwater valves must be fitted in new homes with any fixtures below street level.

How Does a Backwater Valve Work?

The sewer system in your home allows sewage and water to exit the building. If the main sewer line overflows during a storm, a sewer backwater valve will prevent water or sewage from entering your home. Most of the time, you can check through the transparent cover of the access box to ensure it’s functioning correctly.

A small flap within the valve is often open, enabling water to leave your house. It also enables the venting of any sewage gasses. Each side of the flap features a tiny flotation device. These floaters force the flap to rise and close if water or sewage begins to flow back into the house. Thus, keeping everything out of your home.

Once the water stops flowing back toward your home, gravity will allow the flap to fall into the open position. This way, it allows water and sewage to start flowing out of the house once more.

If you are installing a sewer backwater valve in an existing home, you will need a plumbing permit from your municipality. A qualified, licensed plumber will have to cut into the concrete floor, often close to the floor drain. They will then dig down the main sewer line, cut out a section and replace it with the backwater valve.

sewer backwater valve
Inside of a sewer check valve

How to Maintain Your Sewer Backwater Valve

You should check the valve regularly to ensure all moving parts are free to move and clear it of any debris. Most valves have a cover that you can easily remove for cleaning. But take caution! Always wear rubber gloves, then clean around and under the flap with a long-handled brush. The majority of backwater valves come with maintenance instructions from the manufacturer.

Additionally, look at the O-ring surrounding the lid to ensure it is in excellent shape. If not, you need to have it changed to ensure a proper seal. Additionally, examine the floats on each side of the flap and replace them if necessary. If they are worn, they lose their capacity to float. They are also unable to lift the flap when required.

You should also avoid flushing items like diaper liners or “flushable wipes” to keep things running smoothly. When you dispose of these items in the trash rather than the toilet, you may potentially avoid the system being blocked by eliminating the usual sewer clog culprits.

If you’re uncertain about the valve’s condition or if you don’t feel confident trying it yourself, call a plumber to perform an inspection. 

With the right care, your sewer backwater valve should last many years. Follow the manufacturer’s instructions and have the valve inspected and cleaned no less than once a year. Additionally, keeping your system clear of unnecessary materials can increase its lifespan.

Get Help From a Professional

Let sewage backup and basement cleanup be a thing of the past. Our certified and qualified plumbers are always ready to help you fit efficient sewer backwater valves to save you all the effort and cost of sewage backup cleanup.

As NYC’s leading sewer and water main provider, we always have the proper supplies and tools for both big and small projects. As a family-owned business serving NY for over 70 years, we provide response times of 4 hours or less.

Thanks to our GPS-controlled fleet, you can conveniently schedule your appointment within a 2-hour window. You can be sure that we’ll get there on time. Simply put, Balkan is “The Team You Trust”.

Tired of the persistent New York flooding? Do you have a nagging sewage backup problem? Contact Balkan Sewer and Water Main today to handle all your backup valve and plumbing needs!

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David Balkan

David Balkan is the CEO of Balkan Sewer And Water Main, the largest and most trusted service in New York City. David is extremely active in various NYC plumber organizations being the Chairman of the Subsurface Committee in the Master Plumbers Council, and Vice President of the Subsurface Plumbers Association. In addition David’s expertise is respected by officials of New York City agencies such as the NYC DEP, NYC DOB, and the NYC DOT. He frequently provides valuable input on a variety of industry related matters.

Dave Balkan

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