Home Water SOS

Sump pump not working

The pit is filling and the pump isn't keeping up, or isn't running at all. Most failures come down to five spots, and some take a minute to check.

Updated November 2026

Do this first

  1. If water has reached outlets or cords, don't step in it. Cut power to the basement at the panel if you can reach it dry.
  2. Unplug the pump before touching it or reaching into the pit.
  3. Start moving water out: a wet vac or a rented utility pump buys time while you sort out the sump pump.
Five places a sump pump system usually failsCross-section of a basement sump pit. The pump sits in the pit and pushes water up a discharge pipe, through a check valve and out through the foundation wall. Failures happen at the power outlet, the float switch, the intake, the check valve and the outside end of the discharge line.BasementOutside12345
The five usual failure points:
  1. Power: a tripped GFCI outlet, a breaker, or a power cut
  2. Float switch stuck against the pit wall or the pump
  3. Intake clogged with gravel, silt or debris
  4. Check valve failed, so water runs back into the pit
  5. Discharge line frozen, crushed or clogged outside

Check in this order

1. Power

Press the reset button on the outlet and check the breaker. Plug a lamp into the same outlet to see if it works. In a storm, a power cut is the most common reason a sump pump stops, which is why battery backups exist.

2. The float

With the pump unplugged, make sure the float can move freely and isn't caught on the pit wall or the cord. Plug it back in and lift the float gently: the pump should start.

3. The intake

Hums but moves no water? Unplugged, lift the pump and clear debris from the screen at its base. A pump sitting on gravel or silt clogs faster than one on a flat stone or brick.

4. The check valve

If the pit refills right after the pump stops, the check valve on the discharge pipe may be stuck open, sending water straight back down.

5. The discharge line

Follow the pipe outside. Ice, a crushed section or a clogged end means the pump runs but water can't leave. In winter, a frozen line is common.

Repair or replace?

A pump that runs constantly, cycles on and off quickly, hums without pumping after the intake is clear, or is more than about seven to ten years old is usually due for replacement. A plumber can also add a battery backup for storms.

What sump pump work costs

JobTypical cost
Replace a pump in an existing pit$350 – $1,000
New pump, pit and discharge lineabout $1,400
Battery backup pump$150 – $250
Water-powered backup pump$200 – $900
Above-ground discharge pipe$150 – $400
Ranges reported by This Old House, updated March 2026.

Water already on the floor? See water in the basement for finding the source and starting the cleanup.

Sources