Sump Pump Running Constantly: The Seven Causes, in the Order to Check Them

A sump pump that runs constantly, or that starts every minute or two and never seems to catch up, is either moving a lot of water or moving the same water over and over. Both burn out the motor, and the second one is a mechanical fault you can find in ten minutes. The pump was never designed to run without pause; a submersible pump cools itself with the water it moves, and one that runs dry or short-cycles for days is on its way to failing during the storm you bought it for.

This page lists the causes in the order that finds most of them fastest, tells you how to check each with a flashlight and a bucket, and draws the line between what you can fix and what needs a plumber or a drainage contractor. If you have not tested the pump before, the sump pump test covers the safe way to handle a pit with a live pump in it.

Before You Start

Most Likely Causes

1. The float is stuck in the on position. The most common cause and the cheapest fix. A tethered float wedged against the pit wall or the pump body, a vertical float rod bound up with grit, or a float cord tangled with the power cord keeps the switch closed. Check: unplug the pump, lift the lid, and move the float by hand through its full range. It should swing or slide freely without touching anything. Reposition the pump so the float has room, tie cords up out of the way, and clear gravel from the pit.
2. The check valve has failed. Every time the pump stops, water in the vertical discharge pipe falls back into the pit if the check valve does not hold, the level rises, and the pump starts again. That is short-cycling: a run of a few seconds every minute or two, with no rain. Check: watch the pit after the pump stops. If the water level jumps back up within seconds and you hear water pouring back down the pipe instead of a single clunk from the valve, replace the check valve. It is a clamp-on part on the discharge pipe, an easy job with the pump unplugged and a bucket under the joint.
3. The discharge line is blocked or frozen. If the pump runs and the water level does not drop, the water has nowhere to go: a frozen discharge line in winter, a crushed buried section, a clogged outlet screen, or a kinked flexible hose. The pump runs against a dead head and overheats. Check: follow the line outside and confirm water actually comes out while the pump runs. In winter, a freeze-relief fitting near the house lets water escape if the line is blocked.
4. The water table is high, or water is being fed to the pit. After days of rain, in spring thaw, or in a house built on a wet lot, the footing drains deliver water continuously and the pump is doing exactly its job. Check: the pump runs full cycles, the level drops each time, and the outdoor discharge runs steadily. If it runs constantly in dry weather, look for what is feeding the pit: a downspout discharging next to the foundation, grading that slopes toward the house, a neighbor's sump discharging toward you, a broken irrigation line, or, rarely, a leaking supply pipe under the slab. Our gutter guide covers downspout extensions; a water meter that moves with every fixture off points to a supply leak.
5. The float switch is set too low, or the pit is too small. If the on and off points are only an inch or two apart, the pump starts for a few seconds and stops, over and over. A tethered float needs a wide enough pit to swing; a vertical float has an adjustable travel. Check: watch a full cycle and note how far the water drops. Raising the tether length or the float's on point, within the manufacturer's limits, lengthens the cycle. A pit that is too narrow for the pump is a contractor's fix.
6. The pump is undersized or worn. A pump that runs continuously during heavy inflow and barely holds the level, or that moves less water than it used to, is either too small for the house or losing capacity to a worn impeller. Check: during a heavy rain, if the pump never shuts off and the level creeps up anyway, it is undersized or failing. Our sump pump guide covers sizing and why a battery backup matters for exactly this situation.
7. The pump is running dry. A stuck float or a switch that failed closed keeps the pump running after the pit is empty, which destroys it fast. Check: a pump humming with the pit nearly dry. Unplug it immediately and fix the float or replace the switch.

Fix It

• Stuck float: reposition the pump, clear debris, tie up cords, and confirm free travel. Ten minutes, no parts.
• Failed check valve: unplug the pump, loosen the clamps, swap the valve with the arrow pointing up, retighten, and test with a bucket of water. Under an hour.
• Blocked discharge: clear the outlet, thaw a frozen line (never with an open flame), replace a crushed section, add a freeze-relief fitting.
• Float travel too short: adjust per the manual. If the pit is the problem, get a quote for a larger basin.
• Water fed to the pit: extend downspouts, correct grading, fix irrigation, and if the meter shows a leak, call a plumber.
• Undersized or worn pump: replace it with the right capacity for the inflow, and add a backup.

When to Call a Pro

A pump that trips the GFCI, a pit that needs enlarging, a discharge line buried through the foundation that has failed, a suspected supply leak under the slab, persistent water in dry weather with no visible source, and any situation where the pump cannot keep up in a normal rain. A drainage contractor can evaluate whether the footing drains, grading, and pump capacity match the lot; a plumber handles the piping and the electrical receptacle.

Frequently Asked Questions

How often should a sump pump normally run?

There is no normal number. Some pits run every few minutes during a storm and stay dry for months; a house on a high water table may run several times an hour year-round. What matters is that each cycle is a full one, the pump shuts off, and it does not run in dry weather without a reason you can name.

Can a sump pump run continuously without damage?

A submersible pump moving water is cooled by that water and can run for hours in a storm. A pump running dry, or against a blocked discharge, overheats within minutes. Continuous running is a symptom to diagnose, not a state to tolerate.

Why does my sump pump run when it has not rained?

A failed check valve cycling the same water, a stuck float, a high water table, or water being delivered to the pit from a downspout, irrigation, or a leaking pipe. The check valve and float take ten minutes to rule out; the rest is detective work outside.

Should I just get a bigger pump?

Not until you know the pump is the limit. A bigger pump on a stuck float or a failed check valve fails the same way, faster. Diagnose first; if the pump genuinely cannot keep up in a normal rain, size up and add a battery backup.

The Bottom Line

Unplug it, check the float, watch the pit after a cycle to catch a failed check valve, walk outside and confirm the discharge flows, and only then think about water table, float settings, or pump size. Most constant running is a stuck float or a check valve, and both are same-day fixes. A leak sensor beside the pit tells you the moment the pump loses the fight.

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