Sump Pump Not Working? How to Test and Fix It

A sump pump sits in a pit in the basement floor and pumps out groundwater that collects around the foundation before it can flood the basement. It only matters during heavy rain or a fast thaw, which is exactly when you can't afford for it to fail. Test it in the fall before the rain and again in early spring before the snow melts. Most failures are simple to fix.

A float switch stuck against the side of the pit or tangled in the power cord is the most common reason a pump does not turn on. The pump may also be unplugged, or the GFCI outlet or breaker it is on may have tripped. A clogged intake screen stops it from moving water. A failed check valve lets water flow back into the pit, so the pump keeps cycling on and off. In winter, the discharge line outside can freeze or fill with ice and snow. Pumps also simply wear out, usually after 7 to 10 years.

A 20-litre bucket of water for testing, a flashlight, rubber gloves, and a wet/dry vacuum for cleaning the pit. A replacement check valve costs about CAD $15–$40, and a new pedestal or submersible pump about CAD $150–$400. A battery backup pump system and a basement water alarm are worth considering.

1. Make sure the pump is plugged in. If its outlet is a GFCI, press RESET, and check the breaker in the panel.
2. Slowly pour a bucket of water into the pit until the float rises. The pump should start, empty the pit, and shut off.
3. If it doesn't start, unplug the pump and check that the float moves freely and isn't stuck on the pit wall, a cord or debris.
4. With the pump still unplugged, lift it out if you can and clean the intake screen at the bottom of any gravel, silt or debris. Scoop or vacuum out sludge from the pit.
5. If the pump runs but water flows back into the pit when it stops, the check valve on the discharge pipe has failed and needs replacing.
6. Go outside and follow the discharge line to where it empties. Make sure it is not frozen, crushed or blocked, and that it drains at least 2 m away from the foundation toward a spot that slopes away from the house.
7. Plug the pump back in and test it again with a bucket of water.

Many Ontario municipalities prohibit connecting a sump pump to the sanitary sewer, so check your local bylaw before changing where it discharges. The City of Toronto and several other Ontario municipalities offer subsidies toward sump pumps and backwater valves; check your city's current program before you buy. Basement flooding from groundwater or sewer backup is often a separate coverage on home insurance, so check your policy too.

Always unplug the pump before putting your hands in the pit or touching the pump. If the basement is already flooded, do not walk into standing water that may be near energized outlets or equipment; turn off power to the basement at the panel only if you can reach it without standing in water, or call your electric utility.

Call a plumber if the pump hums but doesn't move water, runs constantly even when the pit is not filling, trips the breaker, or is more than about 10 years old. A plumber can also replace the check valve, install a battery backup or a backwater valve, and reroute a discharge line that keeps freezing.