When a septic pump will not start, there are three main areas to check for problems: the electrical system, the pump itself and the controls.

Electricity can be very dangerous, so always use caution when working with electricity and turn off power supply breakers when testing components within the electrical system. If you are not 100% confident you can perform any of these tests safely, call a professional.

Electrical problems

If the pump does not appear to be working at all, does not respond to any tests and is not pumping effluent, there may be a wiring problem. First check your circuit breaker, and then try to use a multimeter or similar device to check wires in the septic system for damage to see what needs to be replaced. 

1. A fuse is blown or circuit breaker is tripped. Check fuses and breakers. Replace fuses as needed. Note the size recommended by the pump manufacturer and pump nameplate rating. Call an electrician to repair the circuit if needed.
2. The pump power cord is not properly wired and is making poor contact. If the system uses a piggyback plug-in, check the pump cord cap prongs for tightness and corrosion. Replace the plug, clean the plug prongs with abrasive paper, or have the electrical receptacle replaced.
3. The branch circuit is wiring too small to carry the pump load. Have the line voltage checked and compare it with manufacturer's specifications. The pump should be plugged into its own circuit breaker (or fuse). If the circuit breaker feeds power to other outlets or appliances, have an outlet installed so that the pump has its own breaker. Call an electrician to repair the circuit.
4. The pump motor overload tripped. Allow the pump to cool for five to 10 minutes, and then reconnect it. If the overload trips again, take corrective action. Have the line voltage checked and compare it with the manufacturer's specifications. Have an electrician or the power company check the branch circuit voltage. Have the pump connected to a separate branch circuit.
5. The voltage provided is too low. Voltage needs to be at plus or minus 10% of motor ratings. Check that sufficient power is getting through the system by reading the voltage at the pressure switch, control box and at any other components that power is running through. If you find that the power is too high or low at the power panel, you may need to contact the power company. Low voltage at the pump will also cause thermal overload and shutdown. Have an electrician repair the circuit and possibly contact the energy provider.
6. Control panel connections and watertightness. Give the control panel a visual exam for obvious signs of defects and wear. Look for loose connections and burnt or melted components. Your previous check of the voltage at the control panel may have already led you to the conclusion that this may be where your problem lies.
7. Bad splice connections or a damaged conduit. Check all electrical splice connections for corrosion and other obvious signs that power is not getting to the pump. Check that the conduit has not been damaged and therefore the wiring along with it (i.e., if it was hit by a lawn mower).

Pump problems

Sometimes the motor to the lift pump may not be working, which means that electricity is still flowing to the pump but it cannot work. At this point, check that the pump is not being obstructed and can operate as designed; otherwise, the pump will need to be repaired or replaced entirely.

1. The impeller is blocked or bound. Disconnect power, remove the pump from the sump, and observe for freedom of impeller and shaft rotation. Clean the volute and impeller, and remove any blockage.
2. The bearings are frozen. Disconnect power, remove the pump from the sump, and observe for freedom of impeller and shaft rotation. Free and lubricate lower bearing of column pump. Contact an authorized service center to replace pump bearing.
3. The water level is not sufficiently high to actuate the control switch. Add water to the sump and observe it turn on. Readjust control floats or weights.
4. An internal motor defect. Remove the pump, disconnect power, connect to rated voltage and actuate the control switch. Contact an authorized service center for repair or replacement.

Float/control problems

If the pump uses a float to detect sewage levels, that float can become stuck or damaged, in which case the pump will not run. Usually you can adjust the float or otherwise fix it to float normally, but you may need to replace the float entirely for more serious problems.

1. The float operation is obstructed or restrained. Add water to the sump and observe it turn on. Readjust the control floats or weights. If it’s attached directly to the pump line, consider installing a separate float tree as it makes pump removal and float operation simpler.
2. The float rod is bent or obstructed by debris. Examine and observe. Readjust the control floats or weights.
3. The float switch is defective. Remove the pump, disconnect power, connect to rated voltage and actuate control switch. Look for deformation, burned or melted components, or a lot of black discoloration. Unplug the pump's cord from the piggyback plug of the float switch. Insert the pump's plug directly into an outlet to test it. If the pump runs, the float switch is bad and needs to be replaced. (Do not leave the pump plugged in too long or it will burn out). Readjust the control floats or weights. Replace the liquid level control. Give the pressure switch a comprehensive visual examination for defects and wear. Switches are key elements to a properly working system, and they are relatively inexpensive.  

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About the author
Sara Heger, Ph.D., is an engineer, researcher and instructor in the Onsite Sewage Treatment Program in the Water Resources Center at the University of Minnesota. She presents at many local and national training events regarding the design, installation, and management of septic systems and related research. Heger is education chair of the Minnesota Onsite Wastewater Association and the National Onsite Wastewater Recycling Association, and she serves on the NSF International Committee on Wastewater Treatment Systems. Ask Heger questions about septic system maintenance and operation by sending an email to kim.peterson@colepublishing.com.

This article is part of a series on troubleshooting pumps:

• Troubleshooting Pumps: The Pump Motor Doesn’t Run
• Troubleshooting Pumps: The Pump Turns On, But There’s No Water
• Troubleshooting Pumps: The Pump Runs Continuously or Cycles Too Frequently
• Troubleshooting Pumps: The Pump Makes a Lot of Noise
• Troubleshooting Pumps: There’s a Sewer Gas Smell