Sump pumps · maintenance
How to test a sump pump: a seasonal checklist
Most sump pumps fail during the storm that needs them, after months of sitting idle. A ten-minute bucket test before the wet season — and after any long dry spell — tells you whether the pump, float, check valve, discharge, backup, and alarm will all do their jobs.
Bottom line
Test in spring and fall at minimum. Pour water into the pit until the pump starts, confirm it empties the pit and shuts off cleanly, listen for the check valve, check the discharge outside, then test the backup and the alarm.
If you do not have a high-water alarm yet, add one such as the Basement Watchdog BWD-HWA — it is the cheapest insurance in the basement.
Safety first
Never reach into the pit with the pump plugged in. Make sure the pump is on a GFCI-protected outlet as local code requires, and unplug it before clearing debris or adjusting the float.
The checklist
- Look before you pour. Check the cord and plug, confirm the outlet has power, and look for debris, gravel, or silt in the pit that could jam the float or block the intake.
- Bucket test the primary pump. Slowly pour water into the pit until the float rises and the pump starts. It should start without humming or delay, pump the pit down, and shut off on its own.
- Watch the float. A tethered or vertical float should move freely without touching the pit wall, the pipe, or the backup pump. A float that sticks is one of the most common failures.
- Listen to the check valve. When the pump stops, water in the discharge pipe should not rush back into the pit. A loud slam, or the pump restarting right away, points to the check valve. See sump pump check valves.
- Check the discharge outside. The line should be clear, sloped away from the house, and free of ice or debris in winter. Water should not run back toward the foundation.
- Test the backup pump. Unplug the primary (or follow the maker’s test procedure) and pour again. The backup should start before water reaches the top of the pit. Check the battery date and terminals. See battery-backup sump pumps.
- Test the alarm. Press the test button or wet the sensor. Replace the battery on a schedule, and confirm phone alerts arrive if you have a Wi-Fi monitor. See sump alarms and Wi-Fi monitors.
- Write it down. Note the date, how the pump sounded, and any parts you replaced. A pump that runs noticeably longer than last season is losing capacity.
What a failed test means
| What you see | Likely cause | Next step |
|---|---|---|
| Pump hums but does not pump | Jammed impeller or failing motor | Unplug, clear debris; replace if it persists |
| Pump never starts | No power, stuck float, or failed switch | Check the breaker and GFCI, free the float |
| Pump runs but never shuts off | Float stuck up, or the pump cannot keep up with inflow or lift | See choosing a primary sump pump |
| Pump restarts right after stopping | Failed or missing check valve | Replace the check valve |
| Backup does not start or runs briefly | Weak or old battery, or tripped backup float | Test or replace the battery |
When to call a pro
- The pump fails the bucket test and you are not comfortable replacing it.
- The pit fills faster than the pump can empty it during heavy rain.
- You need a new outlet, a dedicated circuit, or changes to the discharge line.
Getting help
If the pump fails the test, call a licensed plumber or waterproofing pro; use a licensed electrician for outlets and circuits. R.E. Merrill & Associates has handled industrial and municipal pumps and fluid systems since 1987 — contact R.E. Merrill & Associates with general pump questions.
Related across the site
- Low water pressure on a well — a troubleshooting order for the other basement pump
- Water softener drain air gap — if the softener drains near the sump
Sources
- Zoeller and Basement Watchdog owner’s manuals — periodic pump testing by filling the pit, float clearance, GFCI and unplug-before-service warnings, backup and alarm test procedures.