Condensate Pump Not Working or Leaking? Fixes & Replacement Cost

A condensate pump that stops working is usually clogged with slime, has a stuck float or a bad check valve, or has simply worn out. Cleaning it costs nothing and fixes many of them. A new pump costs $60 to $250 if you buy it yourself, and $150 to $500 to have an HVAC tech install it. Act quickly, because a dead pump can shut off your AC or furnace or flood the floor.

Typical pro cost

$150 to $500

LowHigh

Urgency: Fix within a day or two
DIY difficulty: Easy to moderate
Time to fix: 30 minutes to 2 hours
Prices: US typical range

Last reviewed October 2026

What a condensate pump does, and why it matters

Your air conditioner pulls water out of the air as it cools. A high-efficiency furnace makes water too. On a hot, humid day an AC can produce several gallons. Normally that water drains away by gravity. When the equipment sits in a basement, attic or closet with no drain lower than it, a small pump does the job instead.

It's usually a plastic box about the size of a shoebox, sitting on the floor next to the furnace or air handler. Water runs into a small tank, a float rises, and the pump kicks on for a few seconds to push the water through a thin plastic tube to a drain, a sink or outside.

Because it's small and cheap, most people forget it's there until something goes wrong. When it does, you'll see one of two things: water on the floor, or an AC or furnace that suddenly won't run.

Why your AC stopped: Most pumps have a built-in safety switch. When the tank gets too full, it shuts off the cooling (and sometimes the furnace) to stop a flood. If your AC died on a humid day and the pump is full of water, that switch is probably why.

Signs it's this problem

Water pooling around the furnace or air handler, or under the pump itself
The AC or furnace won't start, or shuts off after a few minutes
The pump hums but no water comes out of the discharge tube
The pump runs every few seconds, even when there's little water
The tank is full to the top and the pump isn't running
A musty or swampy smell near the unit

Common causes

Slime and algae buildup

The most common cause. Warm, dark, wet tanks grow a gooey film that jams the float and blocks the inlet. It builds up faster in humid climates.

Stuck float

The float tells the pump when to turn on. If debris or slime holds it down, the pump never starts and the tank overflows.

Bad check valve

A small one-way valve stops pumped water from draining back. When it fails, water falls back into the tank and the pump runs over and over.

Blocked or kinked tubing

The thin discharge line can kink behind the unit, clog with sludge, or freeze where it exits the house in winter.

No power

An unplugged cord or a tripped GFCI outlet looks exactly like a dead pump. Check this first.

Worn-out motor

Small pumps often last 3 to 7 years. A motor that hums but won't move water, or a cracked tank, means it's time for a new one.

How to fix it, step by step

Put down a towel and keep a bucket and a wet/dry vac nearby. You may spill a few cups of water.

1
Check the power. Make sure the pump is plugged in, then press the reset button on any nearby GFCI outlet. If the pump starts and drains, you're done.
2
Turn the AC or furnace off at the thermostat, then unplug the pump. Never put your hands in the tank while it has power.
3
Empty the tank with a cup or a wet/dry vac. Most lids lift off or unclip. Wipe out the slime and gently move the float up and down until it slides freely.
4
Follow the discharge tube to where it ends. Straighten any kinks, and blow through it or clear it with the wet/dry vac. Outside lines can freeze in winter.
5
Plug the pump back in and slowly pour about a quart of water into the tank. It should switch on, empty the tank and shut off within a few seconds.
6
If it drains but then switches back on every few seconds, the check valve is leaking back. Replace the valve, which costs $10 to $25 and threads in by hand on most pumps.
7
If the motor hums but won't pump, or the tank is cracked, replace the pump. Take a photo of the model label so you can buy one with the same lift height and safety switch.

Safety: Water and electricity sit inches apart here. Unplug the pump before touching the tank, and dry the floor before plugging it back in. If the safety switch wires connect to the furnace control board, leave that wiring to a pro.

Tools and materials

Towels, bucket and a wet/dry vac
Old toothbrush or rag
Mild bleach-free cleaner or a little dish soap
Replacement check valve or pump, if needed

Approximate DIY cost: $0 to $250

Call a pro when

The safety switch is wired into the AC or furnace
The discharge line runs through a wall or ceiling and is blocked inside
There's no outlet near the pump and one needs to be added
Water has soaked drywall, carpet or the ceiling below an attic unit

Condensate pump replacement cost

The pump itself is inexpensive. What you pay a pro mostly covers the trip, the time, and any wiring or tubing work. A straight swap of a basic pump is a short job, so it should land at the low end.

Typical US prices, including labor and parts where a pro does the work
Job	Typical cost
Clean and test the pump (pro service call)	$100–$200
Replacement check valve (part only)	$10–$25
New pump, bought yourself (standard model)	$60–$150
New pump, bought yourself (high-lift or mini-split pump)	$120–$250
Pump replaced by an HVAC tech	$150–$500
Replacement plus new tubing or safety switch wiring	$400–$1,000
New outlet installed near the pump	$150–$300

Ranges are typical US prices compiled by FixHomeCost from published cost guides and retail prices. Emergency and weekend calls in peak cooling season cost more. If you're quoted $800 or more for a basic pump swap with no new wiring or tubing, get a second quote.

How to stop it happening again

Clean the tank and float every spring before cooling season, and again in fall if you have a high-efficiency furnace.
Ask your HVAC tech to check the pump at every tune-up. It takes them two minutes.
Use the drain-line tablets or cleaner your pump maker recommends to slow slime growth.
Make sure the safety switch is actually wired up. A shut-off AC is annoying, but a flooded ceiling is far worse.
If the pump is over 5 years old and you're already paying for a service call, replacing it is often cheaper than a second visit later.

Water dripping inside but the pump looks fine? The problem may be the drain pan or a clogged drain line instead. See our guide to an AC leaking water inside.

Common questions

Why is my condensate pump leaking?

Usually the pump isn't switching on, so the tank overflows. That's often from a float stuck in slime or a blocked inlet. Leaks can also come from a cracked tank, a loose tube fitting, or a failed check valve that lets water drain back.

How much does it cost to replace a condensate pump?

A standard pump costs $60 to $150 to buy yourself. Having an HVAC tech replace it typically costs $150 to $500. New tubing or safety switch wiring can push the total to $400 to $1,000.

Can a bad condensate pump stop my AC from working?

Yes. Most pumps have a safety switch that turns off cooling when the tank is about to overflow. Clean or replace the pump and the AC usually starts again.

How long does a condensate pump last?

Small pumps often last 3 to 7 years. Yearly cleaning helps them last longer. Pumps that run constantly in humid climates wear out sooner.

Can I replace a condensate pump myself?

Often, yes. If the old pump plugs into an outlet and the safety switch isn't wired to the furnace, you swap the pump, reconnect the tubes and plug it in. If the switch is wired into the AC or furnace controls, hire a pro.

Why does my condensate pump keep running?

The most common cause is a failed check valve that lets pumped water fall back into the tank. A float stuck in the up position or a blocked discharge line can also keep it running.

This is general information, not a professional inspection. See how we research costs.