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If you live in an area that gets a lot of sewer backups or heavy rainfall, you may want to install a flood control system. These systems stop sewage from backing up into your home, which can save you from unsanitary damage and expensive repairs. In our article, we’ll tell you how to install a flood control system and share some troubleshooting tips to common issues. In our video, This Old House host Kevin O’Connor and plumbing contractor Dennis Langowski install a flood control system that includes components to create a more robust program.
*Unless otherwise noted, costs in this article reflect an average of prices that our team found from hardware stores like Lowes and Home Depot, and on Amazon.com.
Understanding Flood Control Systems
To prevent sewage from flowing back into your home during heavy rains or sewer system overloads, plumbing contractors install a flood control system, which is also called a backwater valve. The system consists of two main parts:
- Check valves: These valves help the water flow away from your home and close to prevent backflow
- Pumping system: The pumping system moves sewage from your home when the check valves are closed
Flood control systems act as a barrier between your plumbing system and the municipal sewer system. They keep your home safe from floods when it functions properly.
When Systems Fail: In one This Old House project, homeowner Janet discovered just how devastating a failed flood control system can be. Water backed up from the floor drains with such force that it knocked a shelf right off the wall. After the water receded, she measured 42 inches of standing water in the basement. As she explained: “The frustrating thing is that I thought I had a system in place to prevent all of this and obviously it failed.” Her experience underscores why proper installation and regular maintenance of flood control systems are critical.
Types of Flood Control Systems
There are a few types of flood control systems a plumbing contractor may use in your home. We’ll explain each below:
- Backwater valves: Your plumber installs the system directly on the main sewer line
- Ejector pump systems: These use pumps to push sewage out of the home when gravity flow is impossible
- Overhead sewers: Plumbers raise the home’s drain pipes above the flood level in this system
Choosing the Right System
The backwater valve system is the most common type, but your home’s layout, local building codes, and the flood risks in your area will ultimately determine which system you’ll want to install. Speak with a plumbing contractor who can evaluate your needs and help you make an informed decision.
Pro Tip: If you’re relying on a sump pump as your primary defense, make sure you have a backup plan for power outages. As the This Old House team advises, “Usually when you’re flooding, it’s because of a storm, and a lot of times when that happens, electricity goes out” — rendering a standard electric sump pump useless. Consider a battery-operated backup sump pump to keep water moving even when the power is down.
Preparing for Installation of a Flood Control System
Although most homeowners will need to hire a professional to install their flood control system, knowing the process from start to finish will help you prepare for the project. Here are a few things you and your plumber will need to do before installation:
- Ask utility companies to mark underground lines to avoid damage during excavation.
- Clear the work area of any obstacles.
- Locate your main sewer line and determine the best location for the system.
- Obtain permits from your local building department.
This isn’t a do-it-yourself (DIY) project for inexperienced homeowners. We recommend hiring an expert who has in-depth plumbing knowledge. Plumbing contractors can provide valuable guidance about local permits, identify your main sewer line, and mark utility lines.
Pro Tip: When planning your flood control system installation, make sure each pump will have its own dedicated electrical circuit. As one expert explained during a This Old House project, homeowners sometimes plug sump pumps into switched outlets, and when they leave the basement and turn off the switch, they unknowingly shut off the pump. The recommendation: a dedicated 15-amp line for each pump to ensure uninterrupted protection.
Flood Control System Installation Process
The installation process requires an expert who knows the right materials to build a robust system that protects against severe sewage backups effectively. Here’s an overview of the typical installation steps:
- Excavate the area around the main sewer line.
- Remove any existing backwater valve or flood control system.
- Install the new check valve assembly on the sewer line.
- Secure the check valve with flexible rubber couplings.
- Pour concrete around the valve to provide stability.
- Add gravel and sand layers for proper drainage.
- Construct a circular wall around the valve using concrete blocks.
- Install an access cover at ground level for future maintenance.
Pro Tip: Richard Trethewey, This Old House plumbing and heating expert, emphasizes the importance of a check valve in any pump-based flood control system: “Every pump has to have one. You want to make sure the water only goes one way to leave the building.” Before cutting into any existing discharge pipe, he advises disconnecting the electrical first and draining the water above the check valve to avoid getting soaked.
Key Components of a Robust Flood Control System
If you want a high-quality flood control system, there are several components to include during the installation process.
- Bolted access covers: Secure against high-pressure backflows
- Cast iron check valves: More durable than PVC valves
- Concrete reinforcement: Provides stability and prevents shifting
- Double guard system: Two check-valves in series for added protection
- Proper drainage layers: Guarantees the system remains dry and functional
Maintenance and Upkeep of Your Completed Flood Control System
As you can see from the video, a flood control system can malfunction. There are a few steps you can take to maintain your system and reduce the chance of sewage making its way into your home. Here are our tips:
- Clean the check valves to prevent debris buildup
- Inspect the system annually for signs of wear or damage
- Keep the access cover clear of obstructions for easy maintenance access
- Schedule professional inspections every few years for a thorough evaluation
- Test the system periodically to make sure it’s still operating properly
Importance of Regular Maintenance
You can extend your flood control system’s lifespan through regular maintenance. Cleaning, inspecting, and testing will help you find issues early on before they turn into major problems.
Professional Inspections
Although you may want to take the DIY approach to practicing the maintenance tips above, a professional plumber has the know-how to thoroughly evaluate your system. They can identify and address issues that you may not notice during routine maintenance checks.
Common Issues and Troubleshooting a Flood Control System
Although you may maintain your system and hire a professional to inspect it, you could still run into problems. Here are some common issues and their potential solutions:
- Leaking connections: Often resolved by tightening or replacing couplings
- Pump failures: Could indicate electrical issues or worn-out components
- Stuck check valves: May require cleaning or replacement
- Unusual noises: Might suggest debris in the system or misaligned parts
Cost Considerations of Flood Control Systems
If you’ve ever had to clean up water damage, you know how stressful and costly it can be. It’s estimated that the average cost for water damage restoration is $3,786.* To avoid the amount of stress, time, and money it takes to recover, prevention is key.
Installing a backwater valve in new construction can cost between $135 and $1,000, but it’s more expensive to retrofit the system to existing plumbing. The cost of installing a flood control system can vary widely depending on factors such as:
- Excavation requirements
- Local labor rates
- Permit fees
- Quality of materials used
- System type and complexity
That said, the average cost to install a flood control system in your home is $7,500. The price tag may be high, but a comprehensive system with pumps and multiple check valves makes this a worthwhile investment for homeowners, especially those who are at risk for the potential of multiple backwater floods.
*Cost data in this section sourced from contractor estimates used by Angi.
Balancing Cost and Quality
One of the factors that play a role in a flood control system’s cost is the quality of materials. High-quality materials and professional installation cost more, but it often results in more reliable and durable systems. This long-term reliability can save homeowners money by preventing frequent repairs and replacements.
Our Conclusion
Homeowners in flood-prone areas will find a flood control system invaluable. Although it includes a complex installation process and requires the help of a professional plumbing contractor, these systems offer peace of mind and the potential to save thousands on water damage restoration. Regular maintenance and prompt attention to any issues will provide you with reliable protection for your home, possessions, and family.
