Why Is My Sump Pump Running Constantly?

What it usually looks like

• The pump motor hums continuously, even in dry weather
• The pump starts, runs a few seconds, stops, and starts again within a minute
• Water in the pit never drops below the pump intake
• The pump is hot to the touch or has tripped a breaker
• You hear water rushing back into the pit right after the pump shuts off
• The discharge pipe outside is barely trickling while the pump runs

Likely causes, most common first

1. Genuine high groundwater

   During an atmospheric river, a crawlspace on clay soil can take on water faster than one pump can move it. If the pit is clearly filling from the soil and the pump is discharging a strong stream, the pump is simply at its limit. That is a capacity problem, not a defect.

2. A failed or missing check valve

   The check valve holds the column of water in the discharge pipe when the pump stops. Without it, that water falls back into the pit, raises the float and restarts the pump. This creates a tight short cycle and is one of the most common reasons a pump runs itself to death.

3. A stuck or misadjusted float

   Tethered floats catch on the pit wall, the discharge pipe or a cord. Vertical floats bind on their rod when silt builds up. A float stuck up keeps the pump on with nothing to pump; stuck down means it never starts and the crawlspace floods.

4. Undersized pump or pit

   A small pit fills fast and empties fast, so the pump starts and stops constantly. A pump that is too small for the head height, meaning the vertical lift plus the run to the discharge point, works hard and moves little.

5. Blocked or frozen discharge line

   Discharge lines that run outside can clog with silt, get crushed by a vehicle, or freeze solid in a cold snap. The pump runs against a closed pipe, pulls high amps and gets hot. In the January 2024 freeze we found several pumps that had cooked themselves this way.

6. The discharge dumps right back at the foundation

   If the line ends a few feet from the house, the water soaks into the same soil and drains back into the pit. The pump is recycling its own output.

Safe things to check yourself first

• Look in the pit with a flashlight. Is water actually entering from the sides or bottom, or is it mostly draining back from the discharge pipe after the pump stops?
• Lift the float by hand to see if it moves freely, and check that nothing is pinning it.
• Go outside and find where the discharge comes out. Confirm water is flowing strongly while the pump runs and that the end of the pipe is not buried, crushed or frozen.
• Watch the pit level after a cycle. If it rises quickly with a gurgle the moment the pump stops, the check valve is leaking.
• Unplug the pump for a minute if it is hot and running dry, and let it cool. Do not leave it unplugged during a storm.
• Measure how far the discharge end is from the house. Less than ten feet on flat ground usually means the water is coming back.

How we diagnose and fix it

• Measure the inflow rate and the pit dimensions to see whether the pump is undersized or simply overwhelmed in a storm.
• Replace failed check valves with a quiet, full-port model installed at the correct height so the discharge does not fall back.
• Clean or replace the float switch, and set the on and off points so the pump runs a full cycle instead of a few seconds.
• Install a properly sized Liberty submersible pump with a cast iron body when the old pump is worn, undersized or a cheap pedestal unit.
• Reroute or extend the discharge line to daylight away from the foundation, with a freeze-resistant termination so it does not block in winter.
• Add a battery backup pump where outages are common, since a storm that fills your pit is often the same storm that knocks out power.

Questions people ask