Sewer Force Main: How It Works and How to Repair It

The Environmental Protection Agency has estimated that the approximate length of the force main system in the US is 60,000 miles or roughly 7.5% of the wastewater system. While the systems are of great benefit, failure can release millions of gallons of raw sewage into the environment, resulting in health risks and massive clean-up costs. This article defines a sewer force main and examines its advantages, disadvantages, and problems. It also discusses the options for force main repair to address leaking sewer pipes. 

What Is a Sewer Force Main?

Sewer force mains pipelines move wastewater under pressure using a pump or compressor. They are typically found in lift stations to drive wastewater from low elevations, where gravity flow mains supply the wastewater, to higher elevations, where it’s once more moved by gravity flow. 

Some sewer force mains use aeration or chlorination to prevent odor and to help ward off excessive corrosion. There is also a requirement for pressure surge control to ensure that a safe operating pressure is maintained at all times, particularly during lift station start and stop sequences.

What Types of Pipes Are Used in a Sewer Force Main?

Maintaining a high flow rate, handling high pressure, and preventing corrosion are critical requirements for sewer force mains. Iron and thermoplastic piping are typically used to meet these demands.

Ductile and cast iron pipes are often selected for their high strength, greater inside diameters, tight joints, and high flow capacity. In addition, cast iron pipes with glass lining and cement lining are available, as are pipes with polyethylene lining to handle highly corrosive wastewater. Ferrous pipe materials are used in approximately 60% of force mains.

Thermoplastic pipes are made from polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene (ABS), and polyethylene (PE). These materials offer less weight, low hydraulic friction, and are resistant to corrosion and microbial attack. 

Other types of sewer force main pipes include cement-lined steel, asbestos cement, and fiberglass-reinforced epoxy pipe. 

Advantages and Disadvantages of Force Main Sewers

The advantages of force mains include significantly reducing the size and depth of sewer lines. That, in turn, reduces the trenching challenges of reaching 20 feet or more, which requires trench shoring and more expensive excavation equipment. Force mains also can use a smaller diameter pipe than would be needed with gravity flow pipes for the same amount of wastewater. 

The disadvantages include the cost of installing lift stations, frequent cleaning and maintenance, and the potential for pipe damage due to corrosion and pressure surges. In addition, any breach in the pipeline will lead to severe damage and costly force main repair and rehabilitation.

Sewer Force Main Problems

There are three main types of sewer force main problems.

1. Pipeline Buildup. Here solid deposits can build up in the pipe, first reducing the flow capacity and second accumulating into a complete blockage. That same build-up at the bottom of the pipe can be pushed through the pipe, causing abrasion that can wear down the pipe wall. Frequent cleaning is required to address this problem.
2. Pipeline Corrosion. Wastewater generates hydrogen sulfide, which is dangerous to breathe and causes pipeline damage. The damage can come from the conversion of hydrogen sulfide to sulphuric acid due to the presence of moisture. This then causes an acid attack on the pipe. Damage can also come from a direct chemical reaction to iron pipes. Approximately 26% of ferrous pipe force main failures are caused by internal corrosion, with another 19% due to external corrosion. 
3. Pipeline Leaks and Physical Damage. Pipeline buildup can lead to breaks in the pipes and their joints. In addition, pipeline corrosion can generate holes in the pipes from acid attacks. Plus, there is also third-party damage due to digging. This is the cause of almost 20% of ferrous pipe force main failures. For non-ferrous pipes, third-party damage accounts for 37% of failures.

All three problems can lead to leaking sewer pipes. That causes not only a smelly mess but environmental damage. Then comes costly force main repair.

What Is Trenchless Sewer Line Repair?

One approach to force main repair and rehabilitation is digging up and replacing the pipes. However, that can be extremely costly and hugely disruptive. The alternative is trenchless underground pipe rehabilitation, which is the process of restoring aging and deteriorating pipes without digging up the pipes. There are four main types of trenchless technology.

1. Pipe Bursting and Replacement. This involves breaking and expanding the existing sewer line. It is then replaced with another pipe. The broken pieces remain underground.
2. Cured-in-Place Linings. Here a tube is inserted through an existing pipe. That tubing is then bonded to the inside pipe surface.
3. Slip Lining Insertion. This approach inserts a smaller pipe into the existing pipe, providing an easy replacement but with reduced flow.
4. Spray-In-Place Pipe Lining. An epoxy coating is sprayed inside the pipe using high-tech machinery. It bonds in a few hours, sealing the pipe from sewer leaks.

What Are the Advantages of Spray-in-Place Pipe Lining for Force Main Repair?

Spray-in-place epoxy pipe lining offers several advantages over digging and repiping sewer lines.

• Minimal Digging. There’s no need to dig up the entire pipe. Often only a 6×6 foot access pit is needed every 650 feet. In some cases, access through existing manholes is the only requirement. It requires only 5% of the trenching and excavating time needed for repiping.
• Limited Disruption. Spray-in-place epoxy pipe lining plumbing takes roughly 15% of the time required to dig up and replace pipes. It repairs the force main sewer pipe leaks quickly. 
• Safe and Durable. Epoxy spray systems provide a protective barrier between the pipe and sewer wastewater. This prevents any leaks from the pipes and environmental hazards. The life expectancy is roughly 75 years.
• Eases Maintenance. Force main sewer lines can flow more freely, limiting pipeline buildup due to their smooth surface. They also help prevent internal pipeline corrosion.
• Cost-Effective. Repiping is 50% to 75% more expensive than spray-in-place epoxy coating for sewer lines. The cost of digging, removing, replacing, and shutting down the digging locations is substantially reduced.

What Is the Spray In Place Solutions (SIPS) Process?

There are lots of epoxy pipe lining companies. The key to selecting the right one is to examine closely the process they use. It must follow detailed procedures to ensure the lining corrects the problem and lasts for the estimated 75-year lifespan. Here’s the process we use.

1. Pipe Mapping. We map the pipe to verify project details. A robotic closed-circuit television camera examines the entire length of the pipe and identifies all issues.
2. Drag Scraping. A drag scraper, pulled in both directions, removes rust and debris. That also helps return the pipe to its original diameter.
3. High-Pressure Water Jetting. Water jetting is then used to remove any remaining scaling, dirt, and film.
4. Surface Prep Verification. At this point, our robotic closed-circuit camera is used to verify that the pipe has been cleaned sufficiently for the epoxy application.
5. Spin Casting Epoxy Application. A state-of-the-art robotic spin cast system applies the epoxy to the pipe. During the application, the epoxy mix ratio, temperature, and speed of the spray head are continuously monitored to ensure the correct thickness is obtained. 
6. Curing and Final Inspection. The pipe is fully submersible after a brief two to three-hour cure time. Then we conduct a full inspection using the robotic closed-circuit television to verify full coverage. 

Our robotic closed-circuit television camera mapping and inspection system can be particularly helpful for periodic inspections of force main sewer pipes. It can identify any buildup, corrosion, or physical damage leading to leaking sewer pipes.

Why Choose Spray In Place Solutions (SIPS) for Epoxy Lining for Force Main Sewer Pipes?

Plenty of epoxy pipe lining companies exist, but Spray In Place Solutions (SIPS) offers a state-of-the-art, technologically advanced method that far outperforms the competition. So don’t just take our word for it. You can explore our many projects, including our 8” sewer pipe restoration project in North Carolina that provided 2,653 feet of a restored sewer line.

Spray In Place Solutions (SIPS) is certified compliant with ASTM 729. Therefore, you will not need to worry about wildlife being harmed by our materials or processes. We are also certified compliant with NSF/ANSI 61. This means rigorous testing has been done to ensure our epoxy coating is safe for drinking water.

Ready to Get Started With Trenchless Pipe Lining to Fix Your Sewer Pipe Problems?

Are you ready to discuss how Spray In Place Solutions’ (SIPS) innovative process can help you enjoy the advantages of trenchless technology for force main repair? Then fill out our Pipe Lining Questionnaire today to get a quote for your project.