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A small magnetic impellor/rotor A larger ‘open’ impellor/rotor A larger ‘closed’ impellor/rotor
The moving part of the pump is the impellor (sometimes propellor-like), it spins to move the water. It is fixed to the rotor (often a cylinder of magnet or metal), that fits inside the body of the pump. In many pumps (but not all), it can be removed for cleaning or replacement. Check the manufacturer’s instructions for details.
Overheating?
Most modern pumps have a built-in thermal cut-out that turns off the pump if it starts to overheat.
- Switch off the pump for a while. This allows the pump to cool, and the thermal switch to re-set.
- Clear any debris from the strainer, and then try turning the pump back on, it may restart.
Overheating can be caused by clogged strainers; by dirt building up in and around the pump; or by the pump running dry. A thorough clean will often help.
Overheating also results from wear and tear, or scale building up on the rotor and bearings. Some manufacturers sell special cleaners that the pump can be soaked in, and these help to safely loosen the scale.
Wearing out?
The bearings on the rotor will wear, but if caught in time, these parts can often be replaced before the pump becomes damaged beyond repair.
On pumps with small magnetic rotors, the impellor is sometimes linked to the rotor by a plastic ‘clutch’ which can wear out. In this case the pump may still make a running sound, but there is no water movement. If you hold the magnetic rotor firmly, and the impellor blades can spin freely, the rotor/impellor needs replaced.
Pumps may run more noisily or erratically as the bearing wears. Replacing the rotor and bearings may solve the issue. On larger pumps this spare part can be quite expensive, so if the pump is run 24/7 and ageing in other ways (more than 6-7 years old) it might make more sense to replace the pump completely.
Drawing in Air?
If the pump is drawing in air, for example if it has started to run dry, it may also overheat. Some of the more modern pumps have electronic controls that can detect when they draw in air. The pump automatically turns off and then back on again a short while after, to try and expel air bubbles from the system. However, if they have been drawing air in for too long, they often shut down completely. In these cases, turn off the pump at the mains to allow it to re-set, check that the pump is fully submerged, and then switch it back on to see if it will restart. copyright www.watergardensolutions.co.uk
Trip Switch?
All outdoor equipment should be protected by an RCD (Residual Current Device) “trip-switch” which is included on all new house installations, but might be missing on older properties. The RCD can be a switch on your electric distribution board, or a device built into a plug or socket. It is distinguished by a “Test” button.
If a fault has been detected, this switch will trip out, turning off the connected power. Sometimes the switch will trip even if there isn’t a fault - perhaps due to a short power-cut, or a lamp failing at the end of its life. Some types of RCD are “non-latching”, which means that they need to be manually turned back on (or re-set) after any power interruption. © www.watergardensolutions.co.uk
Check if some obvious damage has caused the RCD to trip out e.g. due to a spade cutting through the cable; or rainwater entering a connection; or perishing/swelling of older cables. If the RCD has tripped for no obvious reason, and everyone is safely out of contact with the wiring and the pond, try turning it back on. If the power restarts the pump, perhaps there was no fault. Check that the RCD is functioning correctly, by pressing the test button. It should trip out. It can then be turned back on. ©
If the trip switch cannot be turned back on, because it immediately cuts off the power again, or cuts out again after a short time, then there is a fault with the circuit or the pump. Do not continue to run the pump. Turn off or disconnect the power to that circuit, and get it checked.
Fuse?©
If the power-switch is on, and RCD latched on, but there is no movement from the pump, the fuse in the plug/socket/switchbox may have blown, or the overload trip-switch on the distribution board might have shut off. If fuses/overload-switches trip repeatedly, you must turn off the circuit and have it investigated.
If the pump still doesn’t run even though the RCD and fuse/overload indicate no problem, the pump may have failed. Disconnect the power and get the pump checked. ©
N.B. Mains power is very dangerous if mishandled. Always disconnect the power before handling the pump or working in the pond. If in any doubt about electric wiring or appliances – call in professional help.
Where to get help?
In the UK, your first port of call should be the shop or installer who supplied the pump. They should handle any warranty issues, and may be able to supply spare parts. The more reputable manufacturers often have downloadable copies of the instruction guides on their website, or a help-line to call for advice. If it is an electrical problem with the cabling or junctions, your local electrician should be able to help. ©
What about the fish?
If your fish are used to moving water from a filter, fountain or waterfall, then the failure of the pump might cause problems, especially in hot weather. Ideally fit a temporary backup pump or an economically priced air-pump with airstone (available from specialist aquatic suppliers), whilst you sort out the main pump problem. In the short term, see the FAQ sheet “Help, there is a power failure”
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