A sump pump can run for long periods during heavy rain or snowmelt, but if it never stops after the water level drops, check inflow, the float, check valve, and discharge. Continuous operation wears the motor and can hide a drainage problem. Keep hands and extension cords away from water and limit checks to accessible controls.
See whether water is still entering the pit
If the level rises nearly as fast as the pump lowers it, the unit may be responding to real inflow. Consider rainfall, groundwater, and drainage lines. A sudden change in inflow is a reason to investigate exterior drainage or a leak.
Make sure the float moves freely
With power isolated from a dry location, check whether the float is caught against piping, a cord, or the pit wall. Do not reach into water around energized equipment. A float stuck high can keep the pump commanded on.
Check whether pumped water is returning
A failed check valve or a discharge ending too close to the foundation can send some pumped water back to the pit. Listen for return flow after shutdown and see where the exterior line terminates.
A hot motor or dry running means stop
If the pit is empty but the pump keeps running, smells hot, or makes abnormal noise, shut power off from a safe point. The fault may be in the float, relay, or control; do not let the motor run dry hoping it will correct itself.