A force main is the discharge line for the lift station. The discharge lines of the pumps come together in a manifold and then enter the force main. Air accumulation in force mains can create a problem know a water hammer, which is a high pressure shock wave that travels up and down a force main. This problem is associated with pump check valves slamming, sometimes repeatedly, which causes damage to valves and piping. Air release valves are normally installed at the high points in force mains to automatically blow off accumulated air.
Lift station problems can be summarized in the following four categories:
1. Power [power outage, electrical circuit failure, motor burned out].
2. Control System [pump control failure, telemetry system failure].
3. Pumping System [pump failure].
4. Structural [grit deposits, plugged force main or check valve].
Experience is often the best tool in the operator’s toolbox when it comes to trouble shooting. All but the very simple electrical problems (changing fuses) should be left to a licensed electrician unless proper training has been given to operators. Most lift station failures can be prevented through a well though out preventive maintenance program.
Ground water that enters into the sewer system through broken joints and leaking manhole barrels is referred to as infiltration. Storm water that enters manhole covers and illegal connections like gutter drains routed into house clean outs is known as inflow. Both infiltration and inflow can contribute significant amounts of water to the wastewater collection system. Once in the collection system the I & I becomes wastewater that must be treated by the treatment plant. Some treatment plants become hydraulically overloaded during storm events from inflow or during the spring run-off from infiltration. Because of this the identification and control of infiltration is important to the wastewater collection system operator.