A pond pump that has stopped pumping or lost flow usually comes down to one of a handful of causes, and they are worth working through in order. Start with the pump itself, then the water, then the power.
Did you buy a pond pump, or just any submersible?
This is the first question, and it catches a lot of people. Pond and water feature pumps are rated to run continuously, 24 hours a day. Ordinary submersible drainage or puddle pumps are not, and if one has been left running non-stop in a pond, it may simply have overheated and failed early. If your pump was not a proper pond pump, that is very often the real answer, and the fix is to replace it with one that is built for continuous duty.
Is it blocked, and did you pick the right free passage?
Every pond pump has a maximum solid size it can pass, its free passage. The APP TPS passes 5mm and the TPV passes 19mm. If leaves, string algae or debris larger than that reach the impeller, the pump clogs and flow drops or stops.
Check and clean the strainer and impeller. And ask whether you chose correctly in the first place: a fountain-focused pump with a small free passage in a debris-heavy pond will keep blocking, where a larger free-passage pump would not.
Water level, leaks and airlocks
Most pond pumps are submersible and must stay fully underwater. If the level has dropped, through evaporation in hot weather or a leak in the pond or liner, the pump can start drawing air, at which point flow stops and the motor can overheat.
Check the water level and top up, and look for a leak if it keeps falling. If the pump is submerged but still not moving water, it may be airlocked; tilting it gently underwater usually releases the trapped air.
If you are using a surface-mounted pump, such as the Speroni SWIMM, first check that the filter basket lid is fitted correctly and tightened to create a proper seal. Make sure the suction hose inlet is fully submerged and that the suction hose and fittings are airtight. A non-return valve or foot valve on the suction line can help prevent the pump from losing its prime when it stops. You should also check that the suction lift is within the pump’s stated capability, as surface pumps cannot draw water effectively if the vertical lift is too great.
Power and wear
Confirm power is actually reaching the pump: check the plug, the cable for damage, and whether an RCD has tripped.
Finally, if the pump has given years of continuous service, worn bearings, seals or an impeller can quietly reduce its output, at which point it is nearing the end of its life. Our guide on replacing a pond pump covers what to do next.
