A stormwater backflow valve is a small device that prevents city sewage

A stormwater backflow valve is a small device that prevents city sewage from backflowing into your home when the sewer drain in your basement or on your property gets clogged. These devices come in several styles and are often installed by a licensed plumber. They can be retrofitted onto your existing home or installed during construction.

A backwater valve is an inexpensive and effective way to protect your home against the possibility of a clogged sewer line. It also reduces the risk of a back-up, which can cause flooding and other problems.

Inline Check Valves

A check valve is a simple passive device that allows one-way flow of fluids but automatically closes to prevent any backflow. They rely on a minimum flow velocity or pressure differential to open and close.

Check valves are a vital part of any stormwater backflow valve or wastewater system, and can save money over the long term by reducing the cost of maintenance and repair. They can also be used as a backup to more complex backflow prevention systems, such as flap gates and float-gates.

They are an essential component of a stormwater system and should be considered when designing or retrofitting a system.


The most common type of stormwater check valves, inline check valves, are placed inside the pipe that drains into the stormwater system. The valve slips into the pipe’s inner diameter and is pressed into place with a stainless steel expansion clamp.

When the water in the pipe reaches the valve, it exerts a slight amount of pressure against the sleeve (rubber membrane). This causes the sleeve to fold up and out of the way. This seals against the backpressure and ensures the valve closes silently.

Tidal Intrusion & Salt Sensitive Plants

During high tides, seawater can enter stormwater outfalls and back up to streets during periods of flooding. This creates a nuisance and can damage tidal sensitive vegetation near stormwater drains.

A tidal backflow is also a danger to residents and their homes, as it can flood low-lying areas. This can lead to property damages, debris accumulation and disruption of traffic.

Inline check valves are a preferred method of preventing backflow. They are easy to install, require minimal maintenance and have low head-loss.

Flap Gates

A more complex and costly solution to tidal backflow, flap gates are installed at stormwater outfalls that drain into tidally influenced bodies of water. They need to be periodically maintained to ensure a thorough seal, which prevents backflow.

The City of Charleston has been experimenting with this strategy to manage coastal flooding from its stormwater infrastructure. It has installed over 22 new in-line check valves and intends to further develop the program in West Ashley and other low-lying areas of the City.

The TideflexTM Check Valve is a maintenance-free solution to backflow that has proven itself to be dependable and economical. It is a preferred backflow preventer for many communities across the country, and is a key component of the City’s tidal backflow mitigation plan.