Home › What is a sump pump?
What Is a Sump Pump and How Does It Work?
Some links on this page are affiliate links. If you buy through them we may earn a commission at no extra cost to you. How we make money.
How it works
- Water collects in the pit. NDSU Extension says the sump may be connected to drain tile that drains the footings, under the entire basement, or just the area where the sump sits.
- The float rises. When the water reaches a certain level, the float switch turns the pump on (Boston).
- The pump pushes water out through a discharge pipe into the yard, away from the foundation.
- The float drops and the pump shuts off once the pit is pumped out.
The parts
| Part | What it does |
|---|---|
| Sump pit or basin | Holds the water that drains in. Boston says the basin should be sealed to prevent radon gas from entering the home. |
| Pump | Moves the water out. Two basic types: pedestal (upright) and submersible. See pedestal vs submersible. |
| Float switch | Turns the pump on and off as the water level rises and falls. |
| Discharge pipe | Carries the water outside. It must not be plugged and must direct water away from the house (NDSU Extension). |
| Check valve | NDSU Extension says either type of pump should have one on the outlet pipe so water doesn't flow back into the sump. Water flowing back and forth can make the pump cycle more than needed, which decreases its life. |
| Backup (optional) | A second pump or power source for outages and pump failure. See backup options. |
Sources: NDSU Extension, City of Boston.
How long does one last?
Boston's flood-retrofit page gives a useful life of 7 to 10 years for a sump pump installation. NDSU Extension says a common cause of failure is damaged or rusted bearings in the motor, and another common problem is a float switch that doesn't make good electrical contact. See signs a sump pump is failing.
Do I have one?
Look in the basement or crawl space for a pit or lid in the floor, often with a pipe running up and out through the wall. If you bought the house recently, NDSU Extension says that a new homeowner not familiar with sump pumps should consider calling a licensed plumber to check it before the spring thaw or wet season.
Does your sump pump need a backup?
Answer six quick questions based on the risk factors Ann Arbor, Michigan lists. Get a plain answer and the backup types that fit.
Open the backup checkerCommon questions
What is a sump pump?
NDSU Extension calls a sump with a pump in it the first line of defense against water in the basement for many homeowners. The pump removes water that drains into the sump, which may be connected to drain tile around the footings or under the basement.
How does a sump pump work?
Boston's flood guidance says water is directed into a pit or basin. When it reaches a certain level, a float activates the pump, which pushes the water away from your foundation through a discharge pipe into your yard. When the water is pumped out, the float drops and the pump shuts off.
How long does a sump pump last?
Boston's city estimate for a sump pump installation is a useful life of 7 to 10 years. Consumer Reports says all sump pumps eventually die. Your pump's life depends on how often it runs and how well it is maintained.
Where does the water go?
Out through the discharge pipe, away from the house. Rules vary by city. Boston says sump pumps may not discharge to the city's sanitary sewer, and a dewatering discharge permit is needed to discharge into its stormwater drains. Check with your local building or public works department.
Do I need a backup sump pump?
Not everyone does. Ann Arbor, Michigan says it depends on your situation, and backup systems add expense, maintenance and complexity. Use our backup checker to weigh the risk factors it lists.
Related guides
- Sump pump not working: signs and repair
- Pedestal vs submersible sump pumps
- Sump pump replacement and installation
- Sump pump cost
- Where should a sump pump discharge?
- Why does my sump pump run every 5 minutes?
- How to test a sump pump
- Why does my sump pump smell?
- NDSU Agriculture and Extension: Sump Pumps
- NDSU Extension: Check Your Sump Pump Now (March 14, 2016)
- City of Boston: Flood Retrofits (cost and useful-life figures are the city's estimates)
- City of Ann Arbor, Michigan: Sump Pump Backup Options (PDF)
- Consumer Reports: Sump Pump Backup System Buying Guide (updated March 21, 2025)
Free printable: Sump Pump Fall Check
A ten-minute test before the wet season. Download the one-page PDF now, or get it by email along with a short series of five helpful emails.