Confirm that the power supply is operating properly. In the case of the sump pump, power is supplied by an electrical circuit. Use the circuit tester to confirm that the power supply is not only on, but that the proper voltage is being supplied to the pump motor. If there is no power, check the circuit breaker to be certain it has not been tripped. Other items to check are the outlet, the plug and the wires to see if any of those are worn or damaged.
Turn the pump on manually by activating the float switch. If nothing happens, the problem is either in the pump or in the float switch. If the pump attempts to engage but is unable, this is an indication the switch is working properly. The problem could be in the pump motor, or the pump could be clogged, preventing it from turning properly. If the motor seems to work properly, but no water is removed from the sump pit, the problem is most probably in the drain line.
Remove the pump from the sump pit and check the inlet ports. Check for debris or trash that may have become lodged in the pump, blocking the inlet ports. If the ports are blocked, the pump will be unable to draw in any water and the pit will remain filled with water. Remove any debris from the inlet ports and reposition it in the sump pit.
Remove the screws holding the bottom plate on the sump pump. Hold the pump upside down as you remove the plate. Make sure that the impeller rotates properly, checking for any trash or debris tat may have entered the pump. Also check to be certain the impeller is attached properly to the pump shaft. Once all checks have been completed, reattach the bottom plate and return the pump to the pit.
Inspect the drain line as it leaves the sump pump. There are several likely clog points that need to be checked. The first is where the drain line leaves the pump. The next crucial point is the back-flow valve, which allows water to travel in only one direction, preventing it from flowing back into the sump pit. Other areas of concern are at any elbows or junctions in the drain line. Check the drain line as completely as possible. If available, use a plumber's router to clear the line of any debris or clogs.