The short answer
Each cycle removes the water between the switch's on and off levels. An 18 in round basin holds about 1.1 gallons per inch, so a 6 in switch range moves about 6.6 gallons. If water flows in fast and the range is short, the pump starts every few seconds, which wears the switch and motor. Many installers aim for a cycle of about a minute or more.
Gallons per inch
| Basin diameter | Gallons per inch |
|---|---|
| 15 in | 0.77 |
| 18 in | 1.10 |
| 24 in | 1.96 |
The basin cycle calculator works this out for your basin, switch range and inflow.
Fixing short-cycling
- Use a switch with a longer range, such as a tethered float where the pit allows.
- Fit a check valve so the pipe doesn't drain back into the pit.
- Avoid an oversized pump in a small basin.
- Consider a wider basin; the Liberty P382LE51 uses a 24 in basin for fewer, longer sewage cycles.
Products mentioned
Questions readers ask
How often should a sump pump run?
It depends on inflow; short cycles of a few seconds are a sign the switch range or basin is too small.
How many gallons does an 18 in basin hold per inch?
About 1.1 gallons.