Check This First — It Is Free
Go outside and find where the discharge line actually ends. If it stops within a few feet of the foundation, the pump is delivering water straight back into the ground it just pumped it out of — which drains back to the pit, and the pump runs again. Forever. We find this regularly, it is nobody's fault, and extending the line is frequently the entire fix.
The Other Causes
A failed check valve
The check valve stops the column of water in the discharge pipe falling back into the pit when the pump shuts off. When it fails, every cycle drops that water straight back in, the float rises again, and the pump restarts. The tell is a distinctive rapid on-off-on-off cycle and a gurgling sound after each stop. Cheap to fix and it halves the pump's working life while it persists.
A stuck or badly set float
Floats jam against the pit wall, against the discharge pipe, or against debris. A float that cannot drop leaves the pump running against nothing. Worth looking at before assuming the worst — it is sometimes visible immediately.
A pit that is too small
A small pit fills quickly, so the pump cycles frequently by design. Combined with an oversized pump this produces constant short cycling, which wears the motor out through sheer number of starts.
A genuinely high water table
Sometimes it really is just water. Near the shoreline in Laconia, Alton or around the Suncooks, a persistently high table means the pit genuinely keeps filling. That is the pump doing its job — though it is worth confirming the drainage system is sized for it.
A plumbing leak or a spring
Less common, but a supply leak or a spring discharging under the house will keep a sump busy indefinitely. Worth ruling out if the running is constant and unrelated to weather.
What the Pattern Tells You
| Pattern | Most likely | Fix |
|---|---|---|
| Rapid on-off-on-off, gurgle after each stop | Failed check valve | Cheap — valve replacement |
| Runs, stops, runs again within a minute or two | Discharge returning to the pit, or a small pit | $200–$900 to reroute; pit work varies |
| Runs continuously without stopping | Stuck float, or genuinely constant inflow | Look at the float first — it is free |
| Constant, unrelated to weather | Spring, or a plumbing leak | Investigate before spending on the pump |
| Constant only in spring | Seasonal water table | Normal — but check the system is sized for it |
| Recently started, was fine before | Check valve, float, or something changed outside | Usually the cheap end |
Why this matters beyond the electricity bill: motors are worn out by starting and by running hot, and a pump in this state is using up its life early. It is also giving you no margin — when it does fail, it will fail on a basement that has just demonstrated it genuinely needs a working pump.
Questions
How much electricity is this using?
A sump pump running continuously is a meaningful load — typically several hundred watts, around the clock rather than a few minutes an hour. It is frequently how people first notice the problem, via a bill rather than a basement.
Can I just unplug it between uses?
As a very short-term measure while you arrange a repair, and only if you are certain the basement will not take water meanwhile. As an ongoing arrangement, no — you will forget, and the night you forget will be the night it mattered.
Should I fit a bigger pump?
Only if the diagnosis is genuinely that inflow exceeds the pump's capacity. If the cause is a failed check valve or a recycling discharge line, a bigger pump simply moves the same water around faster and wears out sooner. Fix the cause first.
Does constant running mean it is about to fail?
It means it is wearing out faster than it should. Pumps commonly last seven to ten years and rather less when run continuously. If yours has been running constantly for a season and is already several years old, planning a replacement on a dry Tuesday is considerably better than discovering it during a melt.