How to Repair a Submersible Sump Pump

Submersible sump pumps work under water, inside a sump pit. They mainly use float-triggered switches. Rising water forces the float upwards, triggering the pump. Submersible pumps are more durable than floor sucker, pedestal or water pumps. A sealed chamber at the base of the pump protects and prolongs the life of the motor. Submersible pumps need repairing when faults occur in certain small parts. These tend to be the float switch, impeller or faulty electric wiring. The impeller is a small fan-like part that forces water towards the entrance of the discharge pipe. It can clog, stopping water pumping out of the pit.

Freeing the Float

Repair a Submersible Sump Pump
  1. Unplug the sump pump.

  2. Check if the float is free by using a broom handle to move it. The float is very similar to the one inside a toilet block. It is a light, but rigid, plastic ball attached to a line. It floats on top of rising water, setting off the pump when the water reaches a certain level.

  3. If the float moves freely, then the switch could be faulty and require changing.

  4. Disconnect the discharge pipe and lift the pump out of the sump pit.

Damaged Float Switch

  1. Unscrew the chamber at the top of the pump which protects the switch.

  2. Remove the switch and replace with a new one, carefully following instructions from the manufacturer.

  3. Replace the cap.

  4. Re-immerse the pump and reconnect to the discharge pipe. Switch on and test to see if the pump will work.

Clogged Impeller

  1. Unplug the pump and disconnect from the discharge pipe. Lift the pump out of the pit.

  2. Unscrew the pump base.

  3. Unscrew the chamber holding the impeller and remove it.

  4. Clean the impeller by washing it under clean, running water.

  5. Put the impeller back into its chamber, secure it and re-test the pump.

Broken Electricity Supply

  1. Switch off and unplug the sump pump.

  2. Check that the fuse is still in place inside the plug. If it has popped out, push it back into place.

  3. Change the fuse if the fuse is in place as it has probably blown.

  4. Check for broken or loose wires inside the float switch chamber.

  5. Examine the electric circuit breaker.


  • Always turn off the electricity supply and remove the plug from the socket before examining the sump pump.
  • Wear rubber boots for safety.
  • Always examine the pump with dry hands to prevent electrical shocks.
  • Use the correct sized sump pump for your property. Too small a pump can put pressure on the pump and cause it to burn out through overwork.
  • Call a qualified bonded electrician before undertaking any electrical work you are not qualified to carry out.