How to Test Your Sump Pump
Updated February 20, 2026
Test your sump pump in 10 minutes -- verify it activates, pumps, and shuts off, plus inspect the float switch, check valve, discharge line, and backup system.
Overview
A sump pump that fails during a storm means thousands in basement water damage. The worst part: almost always preventable with a 10-minute test that costs nothing. Most failures happen because the pump sat idle for months, the float got stuck, the check valve failed, or the discharge line froze -- all things a quick test catches. Test every 3 months, always before rainy season.
What You'll Need
Safety First
- Never reach into the pit while the pump is plugged in. Need to inspect or adjust something inside? Unplug first.
- Sealed pit cover? Open carefully. Sealed pits can accumulate radon or sewer gas. Let it ventilate for a minute before you lean over it.
Step-by-Step Instructions
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Visual Inspection of the Pump and Pit
Cover off, flashlight in. Pump upright and level on the pit bottom? Look for debris (gravel, dirt, toys, tools) that could block the intake or jam the float. Push the float up with a stick or long screwdriver -- it should move freely, not stuck against the wall or tangled on the power cord. Power cord plugged directly into a GFCI outlet (no extension cord), not kinked or frayed.
Tip: Check the water level. Dry pit after recent rain? Pump is probably working fine. Standing water at or above the float? The pump may have failed silently. Do the water test immediately. -
Pour Water into the Pit to Trigger the Pump
The core test. Fill a 5-gallon bucket and pour it slowly into the pit. Watch the float as the water rises -- it should trigger the pump. You hear the motor, the water level drops fast, and the pump shuts off when the float falls. That full cycle (water in, pump on, water out, pump off) confirms the pump, float switch, and motor are all working.
Tip: Five gallons not enough? Pour another bucket. Activation level varies. Most pumps kick on when water hits 6-8 inches above intake. If you need more than 15 gallons, the float may be set too high or the pit is unusually large. -
Check the Check Valve
After the pump shuts off, listen. Hear water rushing or gurgling back down the discharge pipe? Check valve has failed or is missing. That means every cycle pumps the same water out and back in -- short cycling that kills the motor. Look at the vertical section of the discharge pipe above the pit. Check valve should be there. No valve? Install one. Valve there but water flowing back? Replace it. $10-20 and the most commonly overlooked maintenance item.
Tip: Quick check valve test: hand on the discharge pipe after the pump stops. Vibration or the sound of backward flow means it is not sealing. A working check valve produces silence -- no backflow, no vibration. -
Verify the Discharge Line Outside
Go outside while the pump is running (helper pours water while you check, or test right after activation). Water should flow freely from the discharge line exit. No flow or weak flow? Line may be blocked, frozen, or crushed. Common culprits: ice, mud dauber nests, dirt, collapsed buried pipe. Discharge point should be at least 10 feet from the foundation, water draining away from the house. Pooling near the foundation? It seeps right back to the pit.
Tip: Fall: check the exit for leaves, mud, animal nests. Winter: check for ice inside the pipe. Line tends to freeze? Install a freeze guard fitting where the pipe exits the foundation -- it pops open to discharge above ground if the main line is frozen. -
Test the GFCI Outlet and Backup System
Press TEST on the GFCI outlet -- it should trip, cutting power. Press RESET to restore. That confirms the safety circuit works. GFCI does not trip or reset? Outlet needs replacing. Battery backup? Unplug the primary pump and pour water in. The backup should activate and pump on battery alone. Check the battery indicator -- most systems have a light or display. Replace the backup battery every 3-5 years even if it looks fine.
Tip: GFCI outlets can trip randomly from moisture or voltage spikes, silently killing your sump pump. Check the outlet every quarterly test. Tripping frequently? Have an electrician look -- could be a wiring issue or a failing motor leaking current.
Pro Tips
- Calendar reminder every 3 months: January, April, July, October. April is most critical -- confirms the pump works before spring rains. January catches winter freeze issues.
- Keep a 5-gallon bucket near the pit specifically for testing. Having it ready eliminates the excuse of not bothering.
- Pump over 7 years old? Replace proactively during a dry spell. A new pump costs $100-250. Emergency plumber during a flood runs $300-500+, plus the water damage.
- Water alarm ($15-25) at the top of the pit as a secondary measure. It screams when water rises above normal activation level -- alerts you to failure before the basement floods.
- After heavy rain, check the pit within 24 hours. Pump ran correctly? Pit should be at normal low level. Full pit or pump running nonstop? Investigate immediately.
When to Call a Pro
Testing never needs a pro. But call a plumber if the pump does not activate during the water test, if it runs but does not move water (impeller or intake issue), if the discharge line is buried and you suspect an underground blockage, or if the GFCI trips repeatedly (electrician). A pump that fails the test should be replaced immediately -- do not wait for the next storm.