Pumps are one of the more expensive components of a swimming pool filtration system. When they are working, the pool is clean and leaf free, but when pool pumps begin to go bad, they can be a source of serious aggravation. A humming pool pump is an unhealthy pool pump. The hum indicates that the motor is unable to turn over. Without a properly functioning motor, the pump cannot do its job. Often, the hum is followed by a complete shutdown of the pump due to overheating.
Dirt or other debris might be jamming the pump motor impeller. If you cannot turn the impeller by hand -- after disconnecting the pump from its power source -- you will need to find the source of the jam and remove it. A jammed impeller is one of the easier pump fixes.
If the voltage to the pump's motor is too low – often caused by insufficient wiring – the pump will not turn over. If you try to run a 220-volt motor on a 110-volt electric line, the pump will just hum.
The pool pump’s start capacitor – a fairly inexpensive part that acts a bit like a back-up battery – might be malfunctioning. If the capacitor is leaking oil or is dusted with a white residue it has gone bad and will need to be replaced.
The lubricant, or grease, in the pool pump motor can be displaced by water through a leak in the shaft seal, allowing the bearing to grind against one another. This can create a screeching or humming noise.