Short answer: turn the AC off, find the capped access port on the drain line near the indoor unit, pour in about a cup of distilled white vinegar, wait 30 minutes, and flush with water. Doing this every one to three months keeps algae from building up. If the line is already fully clogged or keeps clogging, call a pro.
Why Florida drain lines clog
Your AC removes moisture from the air and sends it through a drain line, usually white PVC, to the outside. That warm, wet pipe is a perfect home for algae and sludge, and in Treasure Coast humidity it grows fast. A clog backs water into the drain pan, which can overflow onto your ceiling or floor, or trip the float switch and shut the AC off.
What you need
- About one cup of distilled white vinegar
- A small funnel
- A wet/dry shop vacuum, if the line is already slow
- A flashlight and a towel
Step by step
- Turn the system off at the thermostat. For extra safety, switch off the breaker for the indoor unit too.
- Find the access port. Follow the drain pipe from the indoor air handler. Most have a T-shaped fitting with a removable cap close to the unit.
- Pour in the vinegar slowly through the funnel.
- Wait about 30 minutes so it can break down buildup.
- Flush with a cup or two of water and check that it flows out at the drain's outdoor end, usually near the foundation.
- Replace the cap and turn the system back on.
If the water will not flow, the line may be fully clogged. Attach a shop vacuum to the outdoor end of the drain, seal the connection with a towel or tape, and run it for a minute or two to pull the clog out. Then repeat the vinegar flush.
What not to do
- Do not use harsh drain chemicals made for household plumbing. They can damage AC components.
- Do not mix cleaners. Vinegar and bleach together, for example, release harmful fumes.
- Do not disconnect or bypass the float switch to keep the system running.
When to call a pro
- The line clogs again within weeks of cleaning it.
- Water is coming from somewhere other than the drain, or the pan is rusted or cracked.
- You cannot find the access port, or the indoor unit sits in a tight attic.
- There is water damage on a ceiling or wall already.
Recurring clogs can mean a drain line without enough slope or a freezing coil, and our AC leaking water guide covers those causes. For the full routine, see the Florida maintenance checklist.
If your drain keeps backing up, we connect Treasure Coast homeowners with independent, licensed and insured contractors for AC maintenance and repair. Use the quick form or call (772) 266-5463.
Trade Winds Air is a referral service, not a contractor. Cost figures above are general published ranges for educational purposes; every real number comes from the licensed, insured contractor who inspects your system.