Sump Pump Not Working? Common Causes

When a sump pump stops working, the most common causes are a loss of power, a float switch that's stuck, a clogged or jammed impeller, a failed check valve, or a discharge line that's clogged or frozen. Older pumps also simply wear out. Many of these are quick repairs; a pump near the end of its life usually gets replaced.

This guide walks through the likely causes by symptom, what you can safely check, when to call a plumber and what repairs and replacements typically cost as of 2026.

First, stay safe around the pit

A sump pump sits in water and runs on electricity, so start with safety:

• Don't stand in water and touch the pump, its cord or the outlet. If the basement is flooded, stay out of the water.
• Don't reach for a breaker or main switch through water. If you'd have to walk through water to reach it, leave it for an electrician. The CDC gives the same advice for flooded homes (CDC).
• Unplug the pump before you touch the float or reach into the pit, and only when you're standing somewhere dry.
• Keep children and pets away from standing water and the open pit.

If water is rising fast and the pump isn't keeping up, move valuables up off the floor and call a plumber. If you'd like a quick read on what's likely going on, Check my plumbing walks you through it.

What are the most common reasons a sump pump stops working?

These are the usual causes, roughly from most to least common. A plumber will confirm which one applies; treat this as guidance for narrowing it down.

1. No power to the pump

A pump that won't run at all may simply not be getting power. Fixr notes that a pump may not be receiving power as one of the first things to rule out (Fixr). Common reasons include a cord that's come loose, an outlet that's stopped working or a tripped circuit. Storms are a common culprit, because they bring both heavy rain and power outages at the same time. Fixr notes that a battery can serve as backup power when a storm cuts electricity (Fixr).

2. A stuck or misplaced float switch

The float rises with the water and tells the pump when to turn on. Fixr lists a jammed float switch among the most common sump pump problems. The float can fall out of position or get stuck against the side of the pit or on debris (Fixr).

A stuck float can cause two opposite problems:

• Stuck down: the pump never turns on, even as the pit fills.
• Stuck up: the pump runs nonstop, even when the pit is empty.

3. A clogged or jammed impeller

The impeller is the spinning part that pushes water out. Fixr says it can break, get stuck or get dirty (Fixr). The classic sign is a pump that hums but doesn't move water. The motor is getting power, but the impeller can't turn freely. Gravel, silt and debris in the pit are common causes.

4. A failed check valve

The check valve sits on the discharge pipe and stops pumped water from falling back into the pit. Fixr says that if water flows back into the pit after the pump shuts off, the valve may be damaged, and a faulty valve can also cause loud humming or a pump that runs constantly (Fixr).

5. A clogged or frozen discharge line

If the pipe that carries water outside is blocked, the pump runs but the water has nowhere to go. In cold weather, the outdoor end of the line can freeze. Fixr notes that the line must thaw before the pump can work again (Fixr).

6. An old, worn-out pump

Every pump eventually wears out. Fixr gives these typical lifespans (Fixr):

• Submersible pumps (sit in the water): about 5 to 15 years
• Pedestal pumps (motor above the pit): about 15 to 30 years

Fixr adds that maintenance and exposure to heavy flooding affect how long a pump lasts (Fixr). If yours is near the end of that range and having problems, replacement often makes more sense than repair.

7. Other problems

Fixr also lists clogs, rust, leaks and mold among sump pump issues, plus sulfur odors from a pit that has dried out (Fixr).

What is your sump pump doing?

Matching the symptom to the likely causes can save time.

It won't turn on at all

Likely causes include:

• No power: a loose cord, a dead outlet or a tripped circuit
• A float switch stuck in the down position
• A burned-out motor, especially on an older pump

It hums but doesn't pump water

Likely causes include:

• A jammed or clogged impeller
• A blocked intake screen
• A stuck check valve or a frozen or clogged discharge line

It runs all the time

Likely causes include:

• A float switch stuck in the up position
• A failed check valve letting water flow back into the pit
• Heavy groundwater after a lot of rain, when the pump may truly need to run often

Fixr lists both "running constantly" and a faulty check valve among common repair calls (Fixr).

It turns on and off over and over

Short, frequent cycles are often linked to a check valve letting water fall back into the pit, or a float switch that has shifted out of position (Fixr). A plumber can reposition the float or replace the valve.

It smells bad

A rotten-egg or sulfur smell from the pit can come from a pit that has dried out (Fixr). If the smell could be natural gas, though, leave the house and call 911 or your gas utility from outside (AGA). Our guide to a sewer smell in the house covers other sources of that smell.

What can you safely check yourself?

If the floor is dry and you're not standing in water, these checks are safe for most homeowners:

1. Check the power. Make sure the pump is plugged in. If you're unsure whether the outlet works, plug a lamp into it. If the outlet is dead and the electrical panel is in a wet area, call an electrician rather than resetting anything yourself.
2. Do the bucket test. Pour water slowly into the pit until the float rises. Fixr describes this test: it confirms the float rises and the pump switches on, and it also checks the check valve (Fixr). If the pump starts, empties the pit and shuts off, and water doesn't flow back in, the basics are working.
3. Look at the float. With the pump unplugged, check whether the float can move freely or is caught on the pit wall, the cord or debris.
4. Clear visible debris. With the pump unplugged, lift out loose gravel, leaves or trash from around the pump. Don't take the pump apart.
5. Check the outdoor end of the discharge line. Make sure it isn't buried in snow, frozen, crushed or blocked by leaves.
6. Listen. A hum with no water moving points toward the impeller or the line, which a plumber should look at.

Fixr suggests checking the unit every few months and considering a professional inspection once or twice a year, or after heavy rain (Fixr).

When should you call a plumber?

Call a plumber if:

• The pump hums but doesn't move water.
• The pump won't run and you've confirmed it has power.
• The pump runs constantly or cycles on and off over and over.
• Water flows back into the pit after the pump shuts off.
• The pump is in the later years of its expected life and acting up.
• Water is rising and the pump can't keep up.
• The basement is already flooded. Stay out of the water and don't touch anything electrical.

What will a plumber check?

A plumber will usually look at:

• Power to the pump and whether the motor runs.
• The float switch, and whether it moves freely and is set at the right height.
• The impeller and intake for clogs or damage.
• The check valve, by watching whether water falls back into the pit.
• The discharge line, inside and out, for clogs, freezing or leaks.
• The pump's age and condition, to help you decide whether to repair or replace it.
• Whether the pump can keep up with how much water comes into the pit.

How much does sump pump repair cost?

These are national ranges as of 2026, read on the pages linked. Your quote will depend on the part, the pump and how hard it is to reach.

• Typical sump pump repair: $150 to $500, with a national average of $300 (Fixr).
• Float switch repair: $75 to $125 (Fixr).
• Float switch, valve or impeller replacement: $100 to $150 (Fixr).
• Discharge pipe replacement: $175 to $600 (Fixr).
• Stuck float, humming or not pumping: $100 to $250 (Fixr).
• Clog: $150 to $300 (Fixr).
• Frozen pump or line: $200 to $400 (Fixr).
• Battery replacement: $250 to $500, depending on size and type (Fixr).
• Minimum or call-out fee: $50 to $75 (Fixr).
• Extra for emergency repairs: $100 to $200 (Fixr).

How much does it cost to replace a sump pump?

• Replacing an existing pump (new pump and labor): $350 to $1,000 (Fixr).
• New sump pump installation: $800 to $2,000, with a national average of $1,400 for a new submersible pump and pit (Fixr).
• Adding a battery backup to an existing pump: $150 to $250 (Fixr).
• Water-powered backup pump (unit only): $200 to $900 (Fixr).
• Water alarm: $15 to $30 each (Fixr).

What changes the price?

• The part that failed. A float switch is a small job; a new motor or pump costs more.
• Pump type. Fixr lists submersible repairs slightly higher than pedestal repairs (Fixr).
• Location. Fixr lists crawl space and outdoor repairs at the higher end (Fixr).
• Timing. Emergency and after-hours calls cost more.
• Add-ons. A backup pump, a battery or an alarm adds to the total but can protect you during the next storm.

Should you repair or replace a sump pump?

A repair often makes sense when the pump is fairly young and a single part has failed, like a float switch or check valve. Replacement often makes more sense when:

• The pump is near or past its expected lifespan.
• The motor has burned out.
• Repairs are adding up.
• The pump keeps falling behind during heavy rain.

Fixr says that if repair costs add up or the pump is near the end of its life, replacement may be the better choice (Fixr). Fixr also notes a pump that has been in use for 20 or 30 years may be nearing the time for replacement (Fixr).

Do you need a backup sump pump?

A backup is worth asking about if your basement floods during storms, since storms are when power is most likely to fail. Fixr describes a few options (Fixr):

• Battery backup: runs the pump, or a second pump, when the power goes out.
• Water-powered backup: uses your home's water pressure instead of electricity.
• Combination systems: pair an electric pump with a water-powered one.
• Alarms: sound when water in the pit gets too high, so you know something's wrong.

A plumber can tell you which fits your home and your water setup.

What should you ask a plumber?

• What do you think is causing the problem, and how did you confirm it?
• Is it worth repairing at this pump's age, or should I replace it?
• If I replace it, what size and type do you recommend, and why?
• Should I add a battery backup or an alarm?
• Is the discharge line routed so it won't freeze or send water back toward the house?
• Is there a service-call fee, and does it go toward the repair?
• Can I get the price in writing before you start?
• Is your work guaranteed, and for how long?

How do you keep a sump pump working?

A little attention goes a long way:

• Do the bucket test every few months and before the rainy season.
• Keep the pit clear of debris and the lid on.
• Keep the outdoor discharge line clear of snow, ice, leaves and mulch.
• Know your pump's age so a failure doesn't catch you by surprise.
• Consider a backup or alarm if your basement has flooded before.

If water does get in, our guide on what to do when a pipe bursts covers shutting off water and staying safe around wet floors. And before you talk to a local company, you can use Check my plumbing to see the likely causes and what to ask. For general plumbing rates, see our guide to what plumbers cost.