Check the switch before you buy a pump
A replacement pump costs $400 – $1,200 installed. The float switch that most likely caused the failure costs $15 – $50. That ratio is why this page starts with a diagnosis instead of a purchase: the switch is the component that fails most often, and a pump that hums without moving water is usually a healthy motor attached to a float that has stopped moving.
Unplug the unit, lift the lid and look. Gravel and silt collect in the bottom of a pit over years and jam the float travel. A tethered float wraps itself around the discharge pipe. A vertical float rides a rod that corrosion has roughened. Free the float, scoop the pit clean, plug the pump back in and pour five gallons of water down it. A pump that starts promptly, empties the basin and shuts off cleanly has just told you it is healthy, and the whole diagnosis cost you an hour.
Two more inexpensive parts sit in the same category. A failed check valve at $10 – $30 lets the column of water standing in the discharge pipe drain back into the pit each time the pump stops, so the pump restarts to move the same water and reads as worn out when it is simply working twice. And a pump that spins with a dry discharge is usually air-locked: the small weep hole below the check valve has silted over, or it was left undrilled at installation. Both are five-minute fixes that save the larger bill entirely.
The signs that the pump itself is finished
Sound is the most reliable signal, because it comes from the parts that wear. Grinding, rattling, or a vibration you can feel through the lid and that has grown over a season points at the impeller and the bearings, and those conditions travel in one direction only. Visible rust across the housing says the same thing. So does the pour test: when five gallons fail to start the pump and the outlet, the breaker and the float have all checked out, the motor has reached the end.
| What you observe | Cost of the fix | Most likely cause | What to do first |
|---|---|---|---|
| Hums, but moves no water | $15 – $50 | Stuck or failed float switch | Clear the pit and free the float; replace the switch if travel is fine |
| Runs constantly while the pit stays full | $10 – $30 | Failed check valve draining water back | Replace the check valve before you price a pump |
| Short-cycles on and off every few seconds | $10 – $30 | Missing check valve, or a basin too small for the pump | Fit a check valve; a larger basin beats more horsepower |
| Spins normally while the discharge stays dry | $0 – $40 | Air-locked impeller, silted or missing weep hole | Clear or drill the weep hole below the check valve |
| Nothing happens when you pour water in | $0 – $1,200 | Tripped GFCI, unplugged cord, dead motor | Check outlet and breaker, then the switch, then the pump |
| Grinding or rattling under load | $400 – $1,200 | Worn impeller or bearings | Replace the pump; mechanical noise travels one direction |
| Visible rust on the housing, vibration that has grown | $400 – $1,200 | Corroded housing, worn motor mounts | Plan the replacement for this season |
| Over ten years old and still working | $400 – $1,200 | Age | Replace on your calendar rather than during a storm |
Source: Symptom-to-cause mapping compiled from pump manufacturer troubleshooting documentation and published 2025–2026 service-call cost datasets. Costs are homeowner out-of-pocket for the part where the repair is a DIY-scale fix, and installed cost where a pump swap is indicated. · Last reviewed July 30, 2026 · Reference data · How we compile these figures
What a replacement costs
Installed, $400 – $1,200 covers the pump and the one to two hours a plumber needs to change it, assuming the existing pit, check valve and discharge line are sound. Most of that spread is the unit itself: a thermoplastic 1/3 HP pump sits near the bottom, a cast iron 1/2 HP with a quality switch near the top, and emergency weekend rates lift any of them.
Doing it yourself costs the pump alone: $150 – $600, which breaks down to $150 – $500 for a submersible and $100 – $300 for a pedestal. Sizing, housing material and switch style are covered in depth in our sump pump buying guide. The short version: 1/3 HP suits most homes, and 1/2 HP earns its price under a high water table or a long vertical discharge run.
| Line item | Typical range | Unit | What drives it |
|---|---|---|---|
| Pump replacement, installed (existing pit) | $400 – $1,200 | complete | The pump plus 1–2 hours of labor |
| Submersible pump (unit only) | $150 – $500 | per pump | Sits in the water, quieter, longer-lived |
| Pedestal pump (unit only) | $100 – $300 | per pump | Motor above the pit, cheaper, louder |
| Float switch or switch assembly | $15 – $50 | per switch | Vertical, tethered or electronic |
| Check valve | $10 – $30 | per valve | Worth replacing while the discharge is open |
| Sealed pit lid | $100 – $400 | per lid | Humidity and radon control; easiest to fit during a swap |
| Discharge line extension or reroute | $200 – $900 | per run | Length, freeze relief, code-compliant termination |
| Battery backup added at the same visit | $900 – $2,500 | per system | One trip, one basin opening |
| New pit installation (failed basin) | $1,000 – $3,500 | complete | Slab cutting, new liner, plumbing, dedicated circuit |
| Permit, where a new line or circuit is involved | $50 – $250 | per permit | A straight swap usually needs none |
Source: Compiled from published 2025–2026 plumbing service cost datasets and pump manufacturer retail pricing, normalized to installed cost including labor where marked 'complete' and to retail part cost otherwise. Replacement pricing assumes a sound basin, check valve and discharge line. · Last reviewed July 30, 2026 · Reference data · How we compile these figures
The 7–10 year rule, and why the date belongs on the lid
Most sump pumps last seven to ten years, and less where the pit cycles several times an hour through spring. Age on its own is a legitimate reason to replace. A pump in year nine that has performed perfectly is due, and acting on that is arithmetic rather than caution: a planned swap is a $400 – $1,200 line in your budget on a dry Tuesday, while the same pump failing during the storm that was going to fill the pit anyway is a flooded basement. Remediation of a finished one runs $3,000 – $10,000+, so the scheduled version costs roughly a tenth of the unscheduled one.
Write the installation date on the pit lid in permanent marker the day the new pump goes in. It takes ten seconds and it answers the only question that matters seven years later, whether the person asking is you, a plumber, or a buyer's inspector. Add the model number while the marker is out; it makes the next float switch a two-minute order rather than an afternoon of measuring.
Doing the swap yourself
Budget an afternoon, a bucket, a pipe wrench, and a tolerance for the smell of a sump pit. The sequence is short:
- Unplug the pump at the receptacle and confirm it is dead before your hands go into the water.
- Disconnect the discharge at the union or rubber coupling above the check valve. Keep the bucket underneath — the pipe above the valve is full.
- Lift the old unit out and let it drain into the bucket before it travels across the floor.
- Clean the pit. Scoop out the gravel and silt, because that debris is exactly what will jam the new float.
- Set the new pump level on the floor of the basin, on a brick or the manufacturer's base if the bottom is uneven, and clear of the walls so the float can swing.
- Reconnect the discharge and fit a fresh check valve while the line is open, with the arrow on it pointing away from the pump.
- Check float travel by hand through its full range with the pump still unplugged.
- Plug in and pour. Five gallons into the pit; watch it start, pump and stop. Run it a second time to confirm the shutoff repeats.
Two findings turn this into an electrician's job before it is yours. A receptacle lacking GFCI protection needs one fitted before a new pump goes on it, and improvised wiring — an extension cord run from a freezer circuit, a cord spliced and taped, a receptacle hanging loose off the joist — needs correcting first. A sump pump belongs on its own GFCI-protected outlet, and that is inexpensive work measured against the thing it protects.
When a "replacement" is really a new installation
Three findings change the job entirely, and all three become visible the moment the old pump is out of the pit.
- A cracked or collapsed basin. A split liner, or a pit that is really a hole in the slab with gravel walls, admits silt continuously and undermines the new pump inside a season. Setting a proper basin means cutting concrete, which puts the job in new installation territory at $1,000 – $3,500.
- A discharge line that freezes. A frozen run is a working pump with nowhere to send water. Rerouting or extending it with a freeze-relief fitting and a large open end costs $200 – $900, and it belongs in the same visit as the pump.
- A discharge that dumps against the foundation. Water landing three feet from the wall returns through the footing drain and back into the pit, so the pump moves the same water repeatedly and ages early. Carrying the line well away from the house is the cheapest single thing you can do to make the next pump last its full ten years.
One more case is worth naming. Where a healthy pump runs almost continuously through ordinary rain, the pump is the wrong item to be shopping for — that volume of water is a drainage question, and a second pump simply moves it faster. Decide about backup power at the same time as well: the storm that overwhelms a sump is the storm that drops the power line, and a backup fitted alongside a scheduled swap costs less than a separate visit two years on.
- Sump pump repair cost — every fix priced, and the 50% rule for the repair-or-replace call.
- Sump pump installation cost — pricing a new pit, discharge and circuit.
- Best sump pump — horsepower, housing and switch type, in depth.
- Battery backup sump pump — the part that runs when the power stops.
- Water in the basement — finding where the water actually enters.
- Wet basement repair cost — what the drainage answer costs.