Direct answer: A sump pump that starts and stops every minute is usually short cycling. Most often, water is dropping back into the pit through a bad or missing sump pump check valve, or the sump pump float switch is set too tight or getting hung up.
Most likely: Start by watching the water level in the pit right after the pump shuts off. If the water quickly rises again without new groundwater coming in, suspect backflow from the discharge line first.
You want to separate three lookalikes early: water falling back into the pit, a float that is re-triggering too soon, or a pump that is moving very little water because of a discharge problem. Reality check: a pump that runs every minute will wear itself out fast. Common wrong move: unplugging the pump and forgetting to monitor the pit during wet weather.
Don’t start with: Do not start by replacing the whole sump pump. Rapid cycling is often caused by the check valve, float movement, or discharge setup, not the pump motor itself.
You hear a normal pump run, it shuts off, then the water level climbs back up quickly and the pump starts again.
Start here: Watch for water flowing back into the pit from the discharge pipe after shutdown.
The pump runs briefly, the pit level hardly drops, and the float seems to trigger again almost immediately.
Start here: Check the sump pump float switch travel and make sure it is not rubbing the pit wall, pipe, or power cord.
The cycling is worst during storms or snowmelt, but the pump seems calmer when the ground is dry.
Start here: First rule out normal heavy inflow, then check whether the discharge line is sending water back into the pit.
The motor runs, but discharge outside is weak or inconsistent and the pit does not clear well.
Start here: Check for a restricted, frozen, air-locked, or partially blocked sump pump discharge line.
This is the most common reason a pit refills right after the pump stops. Water in the vertical discharge pipe falls back into the basin and re-triggers the float.
Quick check: After shutdown, listen and watch for a rush of water dropping back into the pit. Then inspect the check valve arrow and connection points on the discharge pipe.
If the float has very little travel, the pump can turn on again with only a small rise in water level. A cord, pipe, or pit wall can also trap the float.
Quick check: Lift and lower the float by hand with power off and make sure it moves freely through its full range without catching.
A partial blockage, frozen section, or poor discharge outside can keep the pump from moving enough water per cycle, so the pit level rebounds fast.
Quick check: Check for strong flow at the discharge point outside and look for kinks, ice, sagging hose, or debris at the outlet.
A failing switch can chatter, trigger early, or cut out before the pit is properly lowered, especially on older pumps.
Quick check: If the float moves freely and the discharge is clear, but the pump still starts and stops at odd levels, the switch itself is a strong suspect.
You need to know whether the pit is truly refilling, the float is misbehaving, or the pump is barely moving water. That one observation saves a lot of wrong parts.
Next move: If you clearly see water fall back into the pit after shutdown, move to the check valve inspection next. If you cannot tell what the water is doing because the pit is turbulent or the cover blocks the view, wait for the next cycle and use a flashlight from a safe position.
What to conclude: Fast refill right after shutdown points to backflow. Very little level change points to float setup or weak discharge. Strong inflow during a storm may be normal, but a one-minute cycle still deserves attention.
A bad or missing check valve is the leading cause of a sump pump that restarts every minute.
Next move: If the valve is missing, backward, leaking badly, or obviously not holding water, that is likely your fix. If the check valve looks correct and the pit does not refill from backflow, move on to the float switch and discharge path.
What to conclude: A healthy check valve keeps most of the vertical discharge water from draining back into the basin. If it does not, the pump keeps redoing the same work every minute.
A float that is trapped, too short on tether, or failing electrically can make the pump cycle with only a tiny change in water level.
Next move: If the float was snagged or badly adjusted and now moves freely with more travel, test the pump again and see whether the cycle length improves. If the float moves freely but the pump still starts and stops at odd levels, the float switch itself may be worn out.
A partial blockage or poor discharge outside can make the pump run often because each cycle removes too little water.
Next move: If clearing the outlet or straightening a hose restores strong flow and longer off-times, keep monitoring through the next few cycles. If the discharge path is clear and the float is fine, but the pump still short cycles, the switch or pump may be wearing out.
Once you know whether the trouble is backflow, float control, or poor pumping, you can fix the actual cause instead of guessing.
A good result: If the pump now runs, shuts off, and stays off until the pit genuinely refills, the short cycling problem is solved.
If not: If the pit still refills immediately, revisit backflow and discharge routing. If the pit cannot keep up with incoming water, move to overflow troubleshooting.
What to conclude: At this point you should have a supported repair path: check valve, float switch, discharge section, or full pump replacement when the pump itself is clearly worn out.
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The usual reason is water falling back into the pit after each cycle. A failed or missing sump pump check valve lets the water in the vertical discharge pipe drain back down and re-trigger the float.
Not usually. Heavy groundwater can make a sump pump run often, but a one-minute on-off pattern is still a sign to check for backflow, a float problem, or weak discharge. Frequent cycling is hard on the motor and switch.
Yes. If the sump pump float switch is snagged, adjusted too tight, or failing internally, it can restart the pump with only a small rise in water level or cut the pump off too early.
Not first. Check the sump pump check valve, float switch movement, and discharge line before buying a new pump. Those are common fixes and cost less than replacing the whole unit.
That points to a bigger problem than short cycling alone. The pump may be undersized, the discharge line may be restricted, or inflow may be overwhelming the system. If the pit is nearing overflow, stay with water control and get help quickly.
Yes. If the line is partially blocked, frozen, or the outlet is buried, the pump may move too little water each cycle. The pit level then rebounds quickly and the float turns the pump back on.