Pro Tips: Servicing Sewage Pumps

A master plumber provides advice on troubleshooting and servicing pumps

Pro Tips: Servicing Sewage Pumps

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The term “sewage pump” is loosely used among plumbers. Even though there are different types of pumps that handle different types of waste or water, most plumbers only mention sewage pumps and sump pumps. In reality, the main categories of pumps include sump pumps, effluent pumps, sewage pumps, and grinder pumps. 

Types of Pumps

Sump pumps are used to discharge groundwater accumulation and should not be pumped into a sewage system. Effluent pumps are used to pump grey water from a septic tank to a drainfield. Sewage pumps are made to pump sewage solids up to 2 inches in diameter, and grinder pumps are made to grind up waste into slurry and pump into a sewage system.

Servicing Pumps

Does the unit come on? Verify that you have voltage using a multi-meter. After you have verified voltage, make sure that the float is not stuck. The side walls of the basin could be preventing the float switch from rising. See if it is possible to reposition the pump and float switch in order to give it free motion to turn on and off. After a period of service the torque of the pump may slowly shift the pump’s position at the bottom of the basin. This is usually an indication that the discharge piping is on a bind. If the discharge piping is on a bind every time the pump turns on and off, the pump will vibrate toward the position of least resistance, which may pin the float stuck against the basin wall. If the float switch gets pinned in the up position, the pump will constantly be on. If the float switch gets pinned in the down position, the pump will not come on at all.

If the float switch is moving free and is working properly but the motor just hums, you have three areas to inspect — you are looking for a clogged/shut off discharge line, a jammed pump, or the lift of the pump is over its limit. Use your best judgment on how to take apart the discharge line and possibly the check valve. This may require some planning, especially if it is located inside of a building. Take the line apart and verify that it is not clogged. If the line is open, then pull the pump. Once you pull the pump, take it outside in an open area, properly clean the pump the best you can, and field test using water. If the pump works fine in your field test, hook the pump back up and test the operation. If at this point the pump continues to hum without pumping sewage, more than likely the lift is over the limit. If that is indeed the case, size a new larger-capacity pump for your specific application.

If the pump seems to be having intermittent problems, randomly turning on or off when no one is running fixtures, there either is no check valve or the check valve has failed and needs to be replaced. If the customer complains about going through a lot of pumps in a short amount of time, that is usually a good sign that the check valve has failed. The constant back feed of discharge water coming back into the pit due to the lack of a working check valve causes the pump to cycle. Motors that constantly turn on/off break quickly.

Lastly, if the pump is operating loudly, check and make sure that the piping is properly secured and not vibrating. If not that, it is probably a broken part inside the pump, in which case return it to the manufacturer for repair or better yet replace the pump.

A Final Thought

When servicing pump systems, especially with adjustable floats, people tend to get too technical in their diagnostics and replace pumps with exact models and exact setups. This is not necessarily a good idea. Often, the depth the pump sits in relation to how the receiver pit is set up, and the height of the float switches are often overlooked. The best way to convey this message is with a true story. I visited a house where the customer had four sump pumps replaced in one year. The sump pump was located in a 30-gallon drum just outside the back porch. Nothing crazy — just a standard sump pump setup. I noticed that the PVC discharge line (underground) had been abandoned and the new discharge was a garden hose run on top of the ground. The homeowner said that the first two guys just replaced the pump, stating it was the manufacturer’s faulty product. The third guy said the discharge line must have been clogged so he abandoned the underground discharge entirely. The last gentleman said that all three men who came before him were ridiculous and that the real issue was that the pump was the wrong size and was “running too long between runs.”

What I actually found was that the pit was too shallow, the incoming drainlines were too low, the discharge hose on top of the ground was cycling back into the pit through the abandoned discharge line underground, the pump was set to high with too high of a float setting (wrong type of float for that situation), and worse yet, the house was located at the bottom geographically. A deep pit was installed, with a basic sump pump system, with appropriate incoming storm heights, with a proper discharge to the city storm system, with the appropriate pump and pump switch heights.

My point is that this system was set up to fail and it did not require one tool to diagnose. It just took someone to think. Sometimes thinking outside your tools is the best way to start the diagnostic process — especially in the world of pumps.

About the Author

Anthony Pacilla is a registered master plumber for McVehil Plumbing in Washington, Pennsylvania. He has 22 years' experience in the plumbing and HVAC trades, and has a bachelor’s in business and economics from Thiel College. 


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