Water leaking from an indoor AC is nearly always a clogged condensate drain line. Your AC pulls gallons of humidity out of Houston air every day, and that water drains through a thin PVC pipe that clogs with algae and slime. When it backs up, water overflows the pan — or trips a safety switch that shuts the AC off. Clearing the line with a wet/dry vacuum fixes the vast majority of these leaks in under half an hour.
Watch how it's done
Video: DIYAroundTheHome. Shown for reference — not affiliated with GetHoustonLeads.
What you'll need
- A wet/dry (shop) vacuum
- Distilled white vinegar
- A funnel or turkey baster
- Towels
- A flashlight
Recommended parts & supplies
- Wet/dry shop vacuum — sucks the clog out of the drain line
- AC drain line cleaning brush — scrubs out algae
- Condensate drain pan tablets — prevents future clogs
- Drain line cleaning kit — attaches to clear stubborn clogs
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Step by step
- 1
Turn the system off first
Shut the AC off at the thermostat before you start, so it isn’t producing more water while you work. Lay towels under the indoor unit to catch drips.
- 2
Find the outdoor end of the condensate drain
Follow the small (usually white) PVC pipe from your indoor unit to where it exits — typically outside near the foundation, or over a utility sink. This dripping pipe is your condensate drain, and the clog is almost always between here and the unit.
- 3
Suck the clog out with a wet/dry vacuum
Hold your shop vacuum hose to the open outdoor end of the drain line, sealing around it with your hand or a rag. Run it for two to three minutes. You’ll usually hear and see a slug of dirty water and algae get pulled free — that’s the clog. This step alone clears most drain leaks.
- 4
Flush the line from the indoor access point
Back at the indoor unit, find the drain line access — often a capped T-shaped fitting near where the pipe leaves the drain pan. Remove the cap and pour a cup of distilled white vinegar (or a vinegar-water mix) through it with a funnel. It kills the algae that caused the clog. Let it sit 30 minutes.
- 5
Empty the drain pan and reset the float switch
Check the pan under the indoor unit. If it’s holding water, sop it out with towels so the float safety switch can drop back down and let the system run. Recap the access fitting.
- 6
Turn the AC back on and confirm it drains
Restart the system and, after 15–20 minutes of cooling, check that water is dripping freely from the outdoor end of the drain line and the indoor pan stays dry. Pouring a cup of vinegar down the line every month or two keeps it from clogging again.
When to call a pro
Call a pro if clearing the line doesn’t stop the leak, if you see rusty water or a cracked drain pan, or if the leak is actually refrigerant (an oily residue on the copper lines rather than clear water). A ceiling that’s already stained or sagging from an attic-unit overflow should be looked at promptly to rule out hidden water damage and mold — something Houston’s humidity makes worse fast.
Get a free quote from a local pro
No obligation — a licensed, insured local River Oaks partner will reach out. Available 24/7 for emergencies.
AC Leaking Water Inside — FAQ
Why is my indoor AC unit leaking water?
How do I keep my AC drain line from clogging?
Is a leaking AC an emergency?
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