How to Troubleshoot a Submersible Pond Pump

Written by ian kelly
  • Share
  • Tweet
  • Share
  • Pin
  • Email
How to Troubleshoot a Submersible Pond Pump
Submersible pond pumps need periodic maintenance for trouble-free operation. (Jupiterimages/BananaStock/Getty Images)

A sudden freeze can crack the casing of a submersible pump. If this happens and you have an older unit that uses oil and coolants, your pond will become contaminated. Oil affects oxygen exchange, and coolants release poisons into the water; consequently many Koi enthusiasts and pond owners prefer the newer oil-less pumps driven by magnetic engines. Although these engines offer trouble-free operation, other factors could cause pump failure. If your pump loses efficiency or stops working altogether, carry out a few troubleshooting steps before calling a technician.

Skill level:
Moderately Easy

Things you need

  • Plastic tub
  • Screwdriver or nut driver
  • New pump impeller (if required)
  • High-pressure hose trigger spray
  • Garden hose

Show MoreHide


  1. 1

    Check the circuit breaker on you electrical panel supplying power to the pump. If it is a Ground Fault Interrupter (GFI) breaker, there will usually be a yellow reset button and a sight window on the switch. If the window is orange-coloured, press the reset button; if there is no sight window or reset button, but the switch is between the "on" and "off" positions, turn the switch off and then back on to see if this corrects the problem.

  2. 2

    Check to see if the pump is plugged into a Ground Fault Circuit Interrupter (GFCI) electrical socket if there is a regular breaker switch on the panel; there will be a test button and a reset button between the two sockets. Unplug the pump and press the button in to reset the GFCI. Plug the pump back in to see if this corrects the problem.

  3. 3

    Unplug the pump if the water level has dropped sufficiently to expose the pump housing. If the pump is hot, the thermal protection device may have tripped. Unplug the pump, refill the pond and wait for about an hour for the pump to cool down; if the unit is fitted with a thermal protection device, it will reset itself. Plug the pump back in after a cool-off period to see if you have corrected the problem.

  4. 4

    Unplug the pump and pull it out of the water. Immerse the pump in a plastic tub with sufficient water to cover the housing. Switch the pump on; if it runs quietly, air may be trapped inside the impeller housing. Rock the pump back and forth with the outlet pointing upward; if bubbles escape, you have solved the problem; but if you hear a humming noise, go to the next step.

  5. 5

    Remove the screws or bolts holding the impeller cover to the pump with a screwdriver or nut driver. Dig out any debris or solid objects jamming the impeller and twist it back and forth to ensure that it moves freely. If the impeller is damaged, replace it by following the directions in the owner's manual.

  6. 6

    Fit a high-pressure trigger to your garden hose, spray the impeller housing clean, and then hose off all debris and sludge from the pump inlet filter. Replace the impeller housing and try the pump out to see if this corrects the problem.

Tips and warnings

  • If the breaker switch trips immediately or the reset button clicks off after you check and reset the electrical supply, there are three possible causes: 1) A faulty pump seal has allowed water into the casing; if this is the case, you must replace the pump. 2) The GFI or GFCI is faulty. 3) There is a short circuit somewhere in the pump wiring. If conditions 2 or 3 apply, call a licensed electrician.
  • If the impeller does not turn freely after you remove jammed debris, the shaft bearing or motor windings have seized up -- replace the pump.

Don't Miss

  • All types
  • Articles
  • Slideshows
  • Videos
  • Most relevant
  • Most popular
  • Most recent

No articles available

No slideshows available

No videos available

By using the site, you consent to the use of cookies. For more information, please see our Cookie policy.