Why Does My Sump Pump Keep Running?
Diagnostic guide for a Brooklyn Park sump pump that won't stop cycling. Five most-likely causes and what each one looks like.
Quick answer
Most often a stuck float, a clogged or failed check valve, an undersized pit for the local water table, a frozen or restricted discharge line, or — less commonly — a genuinely high water table that needs exterior waterproofing. All five are diagnosable in a single visit.
The five causes ranked by likelihood
1. Stuck float (most common)
The float switch tells the pump when to turn on and off. If it's stuck in the "on" position by debris in the pit, a kink in the cord, or contact with the side of the pit, the pump never gets the signal to stop. Quick check: unplug the pump (briefly), lift the float by hand, plug back in — does the pump cycle normally? If yes, the float assembly needs to be cleared, repositioned, or replaced.
2. Failed check valve
The check valve sits on the discharge pipe above the pump. It prevents the column of water in the discharge line from flowing back into the pit when the pump shuts off. When it fails, water backflows, the pit fills again, the pump turns on, and you get rapid short-cycling. Listen near the discharge line a few seconds after the pump shuts off — if you hear flowing water back into the pit, the check valve is the culprit. ~$30 part + 30 minutes of labor.
3. Undersized pit for the water table
Brooklyn Park sits on glacial outwash with a seasonal high water table. A pit that's adequate in dry seasons can be undersized during March-May snowmelt or after summer storms. The pump runs constantly because new groundwater enters faster than the pump can clear it. Solutions: larger pump (higher GPM), larger pit, or an additional pit further from the foundation.
4. Frozen or restricted discharge line
In Minnesota winters, the discharge line that exits the house and runs along the exterior can freeze near the exit point. Water can't leave, gets sent back into the pit, pump cycles repeatedly. Check: is water visibly exiting the discharge pipe outside? If no, freeze is likely. Discharge-line insulation, heat tape on the exit point, or re-routing the line below frost depth all help.
5. Genuine high water table (least common)
If pump + pit + check valve + discharge are all fine and the pit is still filling constantly, it may be persistent groundwater intrusion through the foundation walls or footings. This calls for exterior waterproofing, drain tile installation, or sometimes a structural fix — out of plumbing scope but the diagnosis is the same visit.
When to call
A pump that's been running for hours straight is on its way to burning out — pump motors are designed for intermittent cycling, not continuous duty. If you can't quickly identify a stuck float yourself, call. Sump pump service includes diagnosis + repair + battery backup recommendations in a single visit.
Need a plumber? (763) 309-6542. 24/7 dispatch for active basement flooding.