Definition - What does Force Main mean?
A force main is a pressurized sewer pipe that conveys wastewater in a situation where gravity sewage flow is not possible. Pumps or compressors push the sewage through the force main from lower to higher elevations or across landscapes where deep excavation is not feasible.
Trenchlesspedia explains Force Main
The optimal force in a sewer drainage system is gravity. As wastewater moves from homes or other buildings into the sewer network, gravity lines require no additional power systems to make the sewage flow. Smaller pipes feed into larger ones on the way to the water treatment plant.
But gravity lines don’t always do the trick. Moving the flow uphill requires a pump. Pumping stations are sometimes required in the sewer network to move wastewater along.
Force mains are used in a variety of settings. The most common purpose is to move sewage from low-lying areas. But that’s not always the case. The destination of the wastewater may actually be lower, but the obstacles for excavation might be too great. Sometimes, it turns out that the excavation required to install gravity lines is just too expensive. Under these circumstances, conducting the flow with pressurize force mains may be the best answer.