How to Replace a Sump Pump
Remove your old or failed sump pump and install a new submersible unit to protect your basement or crawlspace from flooding. This guide walks you through disconnecting the old pump, sizing and installing the new one, and verifying it works before the next storm.
What You'll Need
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Tools
Adjustable wrench
For loosening and tightening pipe fittings and discharge line connections.
PVC pipe cutter or hacksaw
To cut the PVC discharge pipe to the correct length during reinstallation.
Utility knife
For cutting a cord notch in the pit cover and general prep work.
Wet/dry shop vacuum
To remove standing water from the sump pit before and after pump removal.
Bucket
For bailing any remaining water from the pit and carrying out the old pump.
Tape measure
To measure the discharge pipe length and pit depth for proper float clearance.
Slip-joint pliers
For gripping and rotating smaller fittings or union nuts.
Flashlight or headlamp
Sump pits are dark; hands-free lighting is essential for seeing inside the pit.
Non-contact voltage tester
To confirm the outlet or circuit is de-energized before handling the pump cord.
Materials
Submersible sump pump
Choose a 1/3 HP pump for most residential pits up to 18 inches in diameter with moderate water inflow; upgrade to 1/2 HP for larger pits, high water tables, or frequent run cycles. Match the discharge port size (typically 1-1/4 inch or 1-1/2 inch) to your existing pipe.
$100-$400
Vertical float switch (if not included with pump)(optional)
Controls automatic pump activation. A vertical float is preferred for narrow pits; wide pits can use a tethered float. Many replacement pumps include one.
$15-$40
PVC discharge pipe (1-1/4 inch or 1-1/2 inch schedule 40)
Rigid PVC to run from the pump outlet up to the check valve and out of the basement. Buy a 5-foot stick - you likely won't need more unless rerouting.
$5-$15
Swing-type or spring-loaded check valve
Installed in the vertical discharge line 12-18 inches above the pump outlet to prevent backflow into the pit when the pump shuts off. Must match your pipe diameter.
$15-$40
PVC couplings and adapters
Used to reconnect sections of discharge pipe or adapt from the pump's discharge port thread to the pipe size. Common sizes: 1-1/4 inch FPT x slip, 1-1/2 inch FPT x slip.
$5-$20
Teflon tape (PTFE)
Two to three rolls of standard white plumber's tape for all threaded connections.
$3-$8
PVC primer and cement kit
Purple primer and clear or gray cement for solvent-welding slip-fit PVC joints on the discharge line.
$10-$20
Discharge line union fitting(optional)
A union coupling installed just above the check valve allows you to disconnect the pump for future service without cutting pipe. Highly recommended.
$8-$20
Battery backup sump pump(optional)
A secondary pump powered by a 12V battery that activates during power outages - the most common time flooding occurs. Strongly recommended for finished basements.
$150-$400
Rubber boots and waterproof gloves
Personal protective equipment for working in and around the wet pit.
$10-$30
Step-by-Step Instructions
Cut power to the sump pump circuit
5 minutes
Go to your electrical panel and locate the breaker that powers the sump pump outlet - it is typically a 15-amp or 20-amp dedicated circuit. Flip it to the OFF position and label it with tape so no one turns it back on while you work. Return to the pump and use a non-contact voltage tester on the outlet or pump cord to confirm there is no live voltage before touching any wiring. Shutting off the breaker before unplugging matters because you may be standing on a damp floor when you reach for the plug. If the receptacle is not GFCI-protected, this replacement is a good time to have an electrician add GFCI protection - current electrical code requires it for sump pump receptacles in basements.
Warning
Sump pumps run on 120V AC power in a wet environment. Never skip the breaker step - water and live electricity is a life-threatening combination. If the sump pump shares a circuit with other basement devices you cannot identify, shut off the entire basement subpanel.
Remove standing water and clear the work area
10-20 minutes
If the pump has failed and the pit is full or the basement has standing water, use a wet/dry shop vacuum to remove as much water as possible from the pit and the surrounding floor before proceeding. Bailing with a bucket is acceptable for smaller volumes. Clear away any stored items within 3 feet of the pit to give yourself room to work. Lay down old towels or plastic sheeting around the pit opening to catch drips during removal.
Pro Tip
Shine your flashlight into the pit and note the pit diameter, the location where the discharge pipe exits the pit wall or lid, and whether there is a pit liner. This information will help you confirm your new pump fits before you discard the old one.
Disconnect the discharge pipe from the old pump
10-15 minutes
Look for the check valve in the vertical discharge line, typically 12-18 inches above the pit. If a union fitting is present just below or above the check valve, unscrew it by hand or with a wrench to separate the pipe without cutting. If there is no union, use a hacksaw or PVC cutter to cut the discharge pipe 6-8 inches above the check valve, leaving yourself enough pipe to glue on a new coupling. Place your bucket directly under the cut point before cutting - the pipe will drain several cups of water when opened.
Pro Tip
Mark the height of the cut on the pipe with a marker before sawing so your new section is exactly the same length. Photograph the existing pipe routing before disassembly.
Remove the old pump from the pit
5-10 minutes
Unplug the old pump's power cord from the outlet (power should already be off at the breaker). Lift the pump straight up out of the pit by gripping the pump body or handle - do not yank on the cord. The pump may weigh 15-30 lbs and will drip water, so have your bucket ready beneath it. Once removed, set it on the plastic sheeting. Inspect the pit floor and liner for cracks, sediment buildup, or debris and scoop out any gravel or silt that has accumulated.
Pro Tip
Note how the float switch was positioned and at what height. You will replicate this orientation on the new pump.
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Track This Project FreePrepare the new pump and set the float switch
15-20 minutes
Unbox the new pump and read its installation sheet for any model-specific instructions. If the float switch is a separate purchase, attach it per the manufacturer's instructions - tethered floats clip to the power cord at the specified height, while vertical and piggyback floats typically clamp to the pump body or discharge pipe. The float must have at least 2-3 inches of clearance from the pit wall in all directions to swing freely. Wrap 3-4 layers of Teflon tape clockwise around the threaded discharge port on the top of the pump, then hand-thread the discharge adapter or first coupling onto the port and snug it with a wrench - do not overtighten PVC threads.
Pro Tip
Measure the inside diameter of your existing discharge pipe before purchasing the pump so you buy the matching port size. Reducers exist but add leak points.
Warning
Do not test-run the pump dry (out of water) for more than 30-60 seconds - most submersible pumps are water-cooled and will burn out without water around them.
Lower the new pump into the pit
5-10 minutes
Hold the pump by its body or molded handle and carefully lower it straight down into the pit, feeding the power cord and float switch cord up and over the edge. Set the pump flat on the pit floor - most submersible pumps have a flat base or legs designed for this. Make sure the pump is centered in the pit and that the float switch hangs or pivots freely without touching the pit wall, the pit liner, or the power cord. Route the power cord up and out of the pit in one smooth curve so it does not pinch the float or restrict pump movement.
Pro Tip
If your pit has a cover or lid, route the cord through the designated cord notch or hole before lowering the pump - it is very difficult to thread the cord through the lid after the pump is in place.
Reconnect the discharge pipe and check valve
20-30 minutes
Measure and cut a new section of PVC pipe to bridge the gap between the pump's discharge adapter and the existing pipe stub or check valve above. Before cementing anything, drill a 3/16-inch weep (relief) hole in the new discharge pipe about 2 inches above the pump's discharge port - below the check valve, angled 45 degrees downward into the pit - so trapped air can escape and the pump cannot air-lock; most pump manufacturers require this. Apply PVC primer to both the pipe end and the inside of the fitting socket, let it flash for 5 seconds, then apply PVC cement to both surfaces and push the fitting onto the pipe with a quarter-turn twist. Hold the joint firmly for 30 seconds. Install the check valve so the arrow printed on its body points upward (away from the pump). If you are adding a union fitting, position it just above the check valve - install it last so you can make final alignment adjustments. Let all cemented joints cure for at least 15 minutes before adding water pressure.
Pro Tip
Check valves are directional - if installed backward, the pump will work against backpressure and burn out prematurely. Double-check the arrow direction before cementing.
Warning
PVC primer and cement are flammable and release fumes. Work with ventilation - open a basement window or run a fan. Keep away from open flames.
Restore power and test the pump
15-20 minutes
Confirm all PVC joints have cured for at least 15 minutes. Plug the pump into its dedicated outlet (do not use an extension cord for permanent installation), then restore power at the breaker. Fill the pit with water using a garden hose until the water level rises to the point where the float triggers the pump - usually 8-12 inches of water depth. The pump should activate automatically, drain the pit rapidly, and shut off cleanly when the float drops. Watch the discharge pipe joints carefully for any drips or seeping during the pump run. Run this test cycle two to three times.
Pro Tip
Listen for the pump to prime quickly and move water within 5-10 seconds of starting. Prolonged running without moving water may indicate an airlock or closed check valve. To re-trigger the pump for another test cycle, add more water to the pit - never run the pump dry and never reach toward an energized pump.
Warning
If the pump runs continuously and does not shut off, the float switch may be stuck or set too high. Shut the breaker off immediately and adjust the float height before leaving the pump unattended.
Secure the discharge line and replace the pit cover
10-15 minutes
Strap or anchor the discharge pipe to the wall using pipe hangers or plastic pipe straps every 4 feet to prevent vibration noise and stress on the joints. Replace the sump pit cover or lid, routing the power cord and any float wires through the designated slots. If the pit cover does not have a cord slot, cut a notch just large enough for the cord using a utility knife - a tight fit reduces radon and odor intrusion from the pit. Recycle the old pump as scrap metal or through an appliance recycler, or follow your municipality's disposal rules.
Pro Tip
Label the breaker in your electrical panel permanently with a piece of tape: 'Sump Pump - Do Not Switch Off.' This prevents accidental shutoff during vacations or power restoration after an outage.
Common Mistakes to Avoid
- Installing the check valve upside-down (arrow pointing toward the pump instead of away), which causes immediate backflow and forces the pump to work against itself on every cycle.
- Skipping the union fitting above the check valve, making future pump removal impossible without cutting the pipe.
- Setting the float switch too low so the pump short-cycles rapidly, overheating the motor and wearing out the switch contacts within months.
- Leaving PVC cement joints under pressure before the cure time (at least 15 minutes, ideally 30), causing joints to blow apart when the pump fires.
- Plugging the sump pump into a shared circuit or using a lightweight extension cord permanently, which can cause voltage drop and nuisance tripping - a dedicated grounded outlet is strongly recommended for sump pumps.
Safety Warnings
- Always shut off the sump pump breaker and verify with a non-contact voltage tester before touching the pump cord or any wiring - water and 120V AC electricity are a fatal combination.
- Never run a submersible pump dry for more than 30-60 seconds; water-cooled motors overheat and fail quickly without submersion.
- PVC primer and cement are highly flammable and produce toxic fumes - ventilate the work area and keep ignition sources (water heater pilot lights, furnaces) away during application.
- Wear rubber boots and waterproof gloves when working in or near a flooded pit; groundwater can carry bacteria, sewage backflow, and chemical contaminants.
- Do not permanently wire a sump pump to an extension cord or power strip; use only a properly grounded dedicated outlet rated for the pump's amperage draw.
When to Call a Professional
Call a licensed plumber if the sump pit itself is cracked or needs to be dug out and re-lined, if the discharge line runs through a finished wall and needs rerouting, or if you discover the pump was wired directly (hardwired) to a junction box rather than plugged into an outlet - hardwired installations require an electrician to disconnect safely and may need a permit. Also call a pro if water is entering the basement through foundation walls or floor cracks rather than the pit; that is a waterproofing or structural issue a sump pump alone cannot solve. If you are in an area with a very high water table and the pit fills faster than you can work, have a plumber install a temporary bypass pump before replacing the primary.
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Frequently Asked Questions
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Project Overview
- Difficulty
- Intermediate
- Time
- 2-4 hours
- Est. Cost
- $150–$550
- Tools
- 9 items
- Materials
- 10 items
- Steps
- 9
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