What you're actually clearing
The condensate drain line is the 3/4-inch PVC pipe that runs from your indoor air handler to a drain outside or under a sink. It carries away the gallons of water your AC pulls from Houston's humid air. When algae, dirt, and scale build up, water backs into the pan and eventually trips the float switch that shuts the system off.
The easiest method first: a wet/dry vac
If your line has an outdoor termination point, the fastest fix is to attach a wet/dry vac directly to it and pull for a minute or two. Make sure you seal the connection — duct tape around the gap works — because the whole point is suction pressure. On most Houston homes this clears a basic clog without opening the unit.
The vinegar or bleach flush
Once water is flowing, pour half a cup of white vinegar (or a diluted bleach solution) down the line to slow regrowth. Vinegar is gentler on the pipe and the environment; bleach is harsher but more thorough. Do this monthly in summer and you'll rarely have a clog. Skip both if you have a condensate pump — route the flush through the cleanout instead.
When the clog is too deep to DIY
If the vac method doesn't restore flow, the clog is likely inside the line or the pan itself is the issue. At that point call a tech — chasing a deep clog with a coat hanger can puncture the pipe or push the blockage into the evaporator cabinet. A pro clears it with CO2 or a line brush and verifies the float switch and pan in the same visit.
Frequently Asked Questions
How often should I clean my AC drain line?
In Houston's humidity, flush the line with vinegar monthly during the cooling season. That prevents the algae and mold buildup that causes most clogs.
Is bleach or vinegar better for a drain line?
Vinegar is gentler and safer for the pipe and drains; bleach is harsher but more thorough. Either works for maintenance; avoid bleach if you have a condensate pump.
Why does my AC keep clogging the drain?
Persistent clogs in Houston usually mean algae regrowth or a drain line that's undersized or improperly sloped. A tech can re-pipe the line and add a cleanout near the coil.
HVAC247PRO is a licensed Texas HVAC contractor (TACLB00105442E and TACLA95904E) serving the Houston metro 24/7. Call (346) 451-1559 or book an inspection online and a technician will be at your door the same day.