Wastewater systems are composed of multiple pipelines with different jobs. One of these is a force main, which plays a vital role in how wastewater is dealt with and discharged through the system. But what exactly are force mains and how do they work? We answer these questions (and more) in this article.
Definition of Force Mains
The US Environmental Protection Agency defines force mains as pipelines that convey wastewater under pressure from the discharge side of a pump or pneumatic ejector to a discharge point.
In simpler terms, a force main is a pressurized sewer pipe. It uses pressure to help move wastewater through a sewage system and is particularly useful in locations where gravity isn’t enough to push the wastewater through. The “discharge point” is where the wastewater leaves the piping system and will normally be a treatment plant.
How Force Mains Work
A force main works by utilizing pumps to move wastewater through a piping system under extreme pressure. The process starts as wastewater is collected (this can be from residential/commercial properties, stormwater, etc.) and flows naturally along the sewage line.
It then reaches a “pumping station” using pumps to pressurize the water and force it through the other side of the force main. Due to the intense pressure used at this point, force main pipes leading from a pumping station are made from extremely durable materials so they don’t burst or crack.
Pressure from the pump continues to force the wastewater all the way through the force main pipes until it reaches a discharge point. From here, the water is then ejected where it will typically end up in a sewage treatment plan. The normal sewage treatment process occurs and clean water can be released back to the environment.
Components
Force mains are primarily comprised of four key elements:
- Pipes – These pipes carry the water through the system and must meet specific criteria outlined by the EPA. They must be durable enough to withstand the pressure and be available in the appropriate sizes and thicknesses. Ductile iron pipe is traditionally used, though PVC pipes are increasingly common.
- Valves – Used to control the flow of wastewater through a force main while also preventing any backflow. This makes them a central component to guarantee wastewater flows in one direction only. Other valves are also used to release pressure from the pumping house, preventing instances where too much pressure builds up and can cause burst pipes.
- Pressure surge control devices – Funnily enough, pressure relief valves are part of many pressure surge control devices used to combat unexpected or extreme pressure changes in a force main. Others include surge tanks to collect water and absorb excess pressure or air chambers. The purpose of these devices is to handle or prepare for pressure surges so the entire pipeline doesn’t get damaged.
- Force main cleaning system – While not technically a “component”, cleaning systems are necessary to maintain force mains and keep them operational. This can involve pipe inspection and cleaning using high-pressure water jets, as well as chemical cleaning where solutions are introduced to the force main to remove grease, limescale, and other deposits.
Applications
There is typically one key application of force mains; they’re used in areas where wastewater systems don’t benefit from gravity acting as a force to help the water flow through the pipes. This will normally be in locations where the system moves from a lower to higher elevation – or if the piping system is completely flat.
In these instances, pressure is needed to pump the water through the pipes or else it’ll either stay stagnant or flow back down with gravity. You can see how this is incredibly important to ensure wastewater is properly moved to treatment centers!
Benefits
One of the major benefits of force mains is that they provide a key wastewater management service when traditional gravity sewer systems don’t work. They deal with a significant problem when treatment centers are at the top of a slope and regular systems are impractical.
Furthermore, force mains are highly useful in transporting large quantities of wastewater in one go. The pressurized system can move the water along a lot faster than natural systems, which is extremely helpful during storms where a lot of excess water flows through the pipes.
We’ve also seen links between force main systems and a reduction in sewage odor from the pipes thanks to maintaining wastewater under pressure and in a more enclosed sewage system.
We hope this article answers all the questions you have about force mains. If you’d like to learn more – or require any services relating to force main installation and maintenance – we’re more than happy to help. Contact Muller today to get started.