How to Fix a Sump Pump That Won't Start

Most sump pump failures are caused by power issues, clogged intake screens, or stuck float switches that can be fixed by checking connections, cleaning debris, and adjusting the float mechanism.

  1. Confirm Power Reaches the Pump. Start with the basics. Make sure the pump is plugged in securely and test the outlet with another device. Check your electrical panel for tripped breakers. Many sump pumps get unplugged during basement cleaning or have loose connections that vibration can work free over time.
  2. Activate the Float Manually. Lift the float switch manually to see if the pump starts. If it runs when you lift the float but won't start automatically, the switch is stuck or needs adjustment. Clean around the float mechanism and make sure it can move freely up and down without hitting the pump housing or pit walls.
  3. Remove Debris from Intake. Unplug the pump and remove it from the pit. Look for the intake screen at the bottom - it's usually a plastic grate or series of holes. Use a brush or hose to remove mud, debris, and sediment buildup. A clogged intake prevents water from entering the pump, making it appear broken when it's just blocked.
  4. Trace Water Flow Downstream. Follow the pipe from your pump to where it exits your house. Look for obvious clogs, kinks, or frozen sections in winter. Pour water into the pit while the pump runs to see if water flows freely through the discharge line. Backflow or slow drainage indicates a blockage downstream.
  5. Rehydrate the Pump System. If your pump has been dry for a long time, it may need priming. Fill the pit with enough water to cover the pump intake. Some pumps have a priming plug you can remove to add water directly to the pump housing - check your manual for specific instructions.
  6. Verify Water Flows One Way. The check valve prevents pumped water from flowing back into the pit. If it's stuck open, the pump will cycle constantly or seem like it's not moving water. You'll hear the pump running but water levels won't drop. Replace a faulty check valve with the arrow pointing away from the pump.