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AC Unit Leaking Water Inside the House

Water dripping from your indoor AC unit is usually a clogged condensate drain line. Clear it in 15 minutes with a wet/dry vac before the water damages your ceiling or floor.

Category:HVAC
Difficulty:Easy
Time:15-20 min
Success:50%
Updated:May 22, 2026

quick_referenceQuick Answer

For AC Unit Leaking Water Inside the House, start with "Find the condensate drain line exit and vacuum it out": Go outside and find where the white PVC drain pipe exits the house — usually near the foundation by the outdoor condenser. It's the pipe that dribbles water when the AC is running. If it's not dripping, it's clogged. Get a wet/dry vac, hold the hose tight against the pipe opening (use a rag to seal the gap), and let it suck for 2-3 minutes. You should hear the vacuum tone change and see a plug of slime and sludge shoot into the canister. Once it's clear, pour a cup of white vinegar down the drain line from the indoor unit to kill the remaining algae. Stop DIY if water has been leaking long enough that the ceiling drywall is sagging or showing mold — this is beyond an ac fix, you need drywall and mold remediation. This is listed as a easy recovery and usually takes about 15-20 min.

verifiedGuide Snapshot

Repair areaHVAC
Estimated time15-20 min
DifficultyEasy
Stop conditions3

Last updated May 22, 2026. Review the stop conditions before continuing.

account_treeRecovery State

DeviceAc Unit
Current stateWater Leaking Inside
Specific stateCondensate Drain Clogged
Failed stepCondensate Drain Operation
Likely failure typeBlocked Path
DIY boundaryDIY recovery first
paymentsCost decision

help1. Understand the Problem

Your AC pulls gallons of humidity out of the air every day. That water drips into a drain pan and flows out through a PVC condensate line. When that line clogs — usually from algae, mold, or dust sludge — the water backs up and overflows the pan. Secondary causes include a cracked drain pan, a disconnected drain line, or the unit being tilted the wrong way. If you've got a ceiling-mounted air handler in the attic, water damage gets expensive fast.

build_circle2. Try This First

Best First Step

Find the condensate drain line exit and vacuum it out

Go outside and find where the white PVC drain pipe exits the house — usually near the foundation by the outdoor condenser. It's the pipe that dribbles water when the AC is running. If it's not dripping, it's clogged. Get a wet/dry vac, hold the hose tight against the pipe opening (use a rag to seal the gap), and let it suck for 2-3 minutes. You should hear the vacuum tone change and see a plug of slime and sludge shoot into the canister. Once it's clear, pour a cup of white vinegar down the drain line from the indoor unit to kill the remaining algae.

visibility3. Visual Guidance

See what's happening and how to try the first recovery step.

1
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Check the drain pan for cracksRemove the front panel of the indoor air handler and look at the drain pan underneath the evaporator coil. Older metal pans rust through, and plastic pans can crack from heat cycling. Shine a flashlight into the pan and look for rust holes, cracks, or water stains trailing down from a split. A cracked pan can sometimes be patched with epoxy rated for wet surfaces, but on units over 15 years old, a replacement pan may not be available.
2
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Make sure the unit is level or tilted correctlyThe air handler should be tilted slightly toward the drain outlet — about a quarter bubble off-level on a spirit level. If the unit has settled or the mounting has shifted so it tilts away from the drain, water pools on the wrong side and overflows when the pan fills. Loosen the mounting bolts, shim with washers, and re-tighten.
3
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Clean the drain line access port and add a float switchMany drain lines have a T-vent with a cap near the indoor unit. Pop the cap and pour a 50/50 mix of hot water and vinegar down the line. If you don't have a float switch in the secondary drain port, install one — it's a $15 safety device that shuts the AC off if the drain backs up again, saving you from ceiling damage.

autorenew4. If That Doesn't Work

Try the next recovery options.

air
Use compressed air to clear a stubborn clogIf the vacuum doesn't pull the clog out, try a can of compressed air or a CO2 drain gun from the inside T-vent. Seal the opening around the nozzle with a rag and give it a short blast. Be careful — too much pressure can blow apart loose PVC joints.
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pump
Install a condensate pump if gravity drain isn't workingIf your drain line runs uphill or across a long horizontal span that keeps clogging, install a condensate pump. It collects water in a small reservoir and pumps it out through a 3/8-inch vinyl tube that can run wherever you need it, even up and over obstacles.
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Frequently Asked Questions

How often should I clean my AC condensate drain line?expand_more
Twice a year — once at the start of cooling season and once mid-summer. Pour a cup of white vinegar or a drain line cleaning tablet into the T-vent access. This prevents the algae sludge from forming in the first place.
Can I use bleach to clean the condensate line?expand_more
Don't use bleach. It can corrode the metal drain pan and the fumes can get pulled into your ductwork. White vinegar kills the algae just as effectively without the corrosion risk.
Why is water leaking from my AC when the filter is clean and the drain line is clear?expand_more
Check that the evaporator coil isn't freezing up intermittently — a thawing ice block releases more water than the drain pan can handle. Low refrigerant, a dirty coil, or a failing blower can all cause intermittent freezing that looks like a drain problem.

warning5. Stop DIY If

Don't continue if any of these apply.

reportWater has been leaking long enough that the ceiling drywall is sagging or showing mold — this is beyond an AC fix, you need drywall and mold remediation.
reportThe drain pan is a rusted metal pan on a 20+ year old unit — replacement pans are often discontinued for units this old.
reportElectrical wiring or connections inside the air handler are wet or show signs of water contact.
Still stuck?Get personalized help with AI Recovery.

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Same Device Recovery States

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Similar Failure Pattern

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This page provides general DIY guidance.
If you're unsure, it's always best to consult a professional.