When the pump will not stop running or keeps cycling, there are two main areas to check: the pump and the tank, or piping problems.   

Don't forget to 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. A cycle counter or running time clock should be installed on the pump for troubleshooting.

1. If the pump will not stop running:

• The soil treatment area may be saturated – In situations where the drainfield is saturated and not taking effluent, the pump line may not be delivering a dose. Check for excessive ponding in the soil treatment area. In the short term, pump the tanks and allow the area to dry out. System repair or replacement may be needed.

• Float problems – Observe and check the float or weight freedom. Clean control floats or weights. Add water to the tank and observe turn-on. Readjust the control floats or weights. If the float rod is bent or obstructed by debris, readjust the control floats or weights.
• The impeller is loose on the shaft – Disconnect power, remove the pump from the dosing tank and observe for freedom of impeller and shaft rotation.
• Water inflow is excessive – Determine if surface or groundwater is entering the system or if there’s a leak in the facility. If not, a larger pump or tank may be needed.
• A clogged screen or pump inlet – Examine and observe, and clean the screen.  
• The pipe discharge is closed by an obstruction or frozen – Clean, snake or jet the discharge line. Replace the pipe if needed.
• Inadequate discharge pipe diameter – Measure the discharge pipe and compare with the manufacturer's suggested diameter (it should be no smaller than the pump discharge). Have a larger-diameter discharge piping installed.
• A defective or inoperative check valve – Clean the check valve; replace the check valve if required.
• A check valve is installed in the wrong direction – Observe the arrow on the check valve indicating direction of flow and change direction if needed.
• Too high of a static and friction head – If the discharge pipe length is extremely long, the friction losses may exceed pump capacity. Observe the number of pipe fittings and reducing bushings. Remove excessive reducing pipe fittings and elbows, and increase the discharge pipe or install a larger pump.

2. Do you have a pump that cycles on and off more than once a minute or once an hour? If the pump cycles too frequently:  

• The soil treatment area may be saturated – In situations where the drainfield is saturated and not taking effluent, the pump line may not be delivering a dose. Check for excessive ponding in the soil treatment area. In the short term, pump the tanks and allow the area to dry out. System repair or replacement may be needed. 
• Water inflow is excessive – Determine if surface or groundwater is entering the system or if there’s a leak in the facility. If not, a larger pump or tank may be needed.
• A defective or inoperative check valve – Observe the backflow of water from the discharge and clean the gate of the check valve or install a new check valve.
• No check valve in high head installations – Examine and observe, and install check valve (be careful in cold climates).
• Floats or weights are improperly adjusted – Add water to the tank and observe turn-on. Readjust control floats or weights.
• Tank size is too small or pump too large for tank – Measure the tank width and depth and compare with design/code recommendations. Install a smaller pump or install a larger dosing tank basin.

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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