My Pond Pump Is Running but the Impeller Is Not Turning

Debris

• In some installations using submersible pumps, only a small pre-filter screen over the pump intake shields the pump from suspended debris. Leaves and large pieces of debris can lodge in the screen and block water flow. Pieces of tough debris small enough to pass through the screen often circulate through the pump without causing trouble. Occasionally, a bit of litter jams between the impeller and its housing, stopping the pump. Skimmer systems take water from the pond surface and separate an on-shore pump from debris with a separate filtration chamber. Both types of pre-filters need regular cleaning to operate properly.

Air-Locks and Priming

• Pumps with flexible impellers start without priming even without water in the pump. Centrifugal impeller pumps usually require priming if located above the water level. Placing a pump closer to the water reduces priming problems. The centrifugal impeller pump needs water around the impeller blades to create flow. On some pumps, pouring water into a priming chamber provides enough liquid to start the water moving through the system. If an air pocket forms around the impeller, flow stops. Lifting the intake slightly, or rocking the pump, often moves the air out of the impeller chamber, according to the Natural Waterscapes website.

Jammed Impellers

• If cleaning filters and removing air-locks fail to restore water flow, disassemble the pump to check the impeller, following the instructions in the owner's manual. Always disconnect power before working on a pump. Check all parts of the impeller housing for debris, and flush the assembly clean with a garden hose. Check the impeller for damage. If you turn the impeller by hand, you should feel resistance from the pump motor. If the impeller shaft won't turn, the problem lies inside the motor housing. Disassembling the motor housing might void the warranty, so call a professional for service.

Magnetic Drive

• Magnetic-drive pumps turn impeller shafts by magnetic force, with no mechanical connection. The motor in a magnetic-drive pump stays sealed in a waterproof housing and requires no service. A buildup of hard-water scale on the impeller shaft can stop the impeller from turning in its socket. Pull the entire impeller assembly out of the housing to check the shaft for damage or mineral deposits. Cleaning the impeller shaft should restore the pump to good working order. Replace the entire impeller assembly if you find damage, recommends Danner Manufacturing. Storing the pump with water in the chamber can cause scale buildup, so drain the pump completely at the end of each operating season.