AC Drain Line Clogged? Prevent Water Damage & Shutdowns
A clogged condensate drain can flood your furnace, trigger emergency shutdowns, and invite mold. Learn how to clear blockages safely and how our technicians provide long-term protection for Portland homes.
Priority service for maintenance plan members. Serving Portland, Beaverton, Wilsonville, and surrounding areas.
Owner & Lead HVAC Technician
Quick Answer
Stop the Leak Before It Grows
Follow this checklist to mitigate water damage and clear minor clogs safely. If the system shuts down or water continues to overflow, our technicians provide thorough drain cleaning and mold prevention services.
Turn the thermostat to OFF to stop cooling and prevent further water buildup.
Switch the fan to ON to help evaporate moisture while waiting for service.
Check the condensate drain pan under the coil for standing water; vacuum it out if possible.
Use a wet/dry vacuum on the outdoor drain line to pull out clogs (attach at the drain termination).
Replace filters to improve airflow and reduce future condensation.
Schedule professional service for cleaning, float switch testing, and mold prevention.
Why AC Drain Lines Clog in Portland
Portland’s moist climate accelerates algae growth inside drain lines. Combine that with pollen, dust, and occasional wildfire smoke, and you have the perfect recipe for clogs. Here are the most common culprits and what we do to eliminate them.
Algae and Biofilm Growth
Warm, moist drain lines create ideal conditions for algae and slime. Without regular cleaning, the drain line clogs and water backs up.
- •Treat the drain line with condensate pan tablets during cooling season.
- •Technicians flush the line with pressurized nitrogen or pump and install cleanout tees for future maintenance.
Improper Drain Line Pitch
Drain lines must slope 1/8 inch per foot. Settling homes or poorly supported lines in crawlspaces lose pitch and trap water.
- •Re-secure drain lines with hangers to maintain proper slope.
- •Install secondary float switches to shut the system down before overflow occurs.
Clogged Condensate Trap
Most high-efficiency systems include a trap to maintain negative pressure. Dust and debris collect in the trap, creating blockages.
- •We disassemble, clean, and reassemble traps each maintenance visit.
- •Homeowners should avoid removing traps without guidance; improper reassembly breaks the water seal.
Failed Condensate Pump
Basement or interior air handlers use pumps to move water to the exterior. Pump failures trigger float switches that shut the system down.
- •Listen for pump operation; silence indicates failure.
- •Replacement pumps cost $250-$450 and include full drain cleaning.
Frozen Evaporator Coil
Ice from low refrigerant or restricted airflow melts and overwhelms the drain pan, spilling water into the furnace cabinet.
- •Address underlying airflow or refrigerant issues to prevent recurrence.
- •Install float switches to shut down equipment when water levels rise.
Debris in Exterior Drain Termination
Drain lines exiting the home may clog with mulch, soil, or insect nests. Portland’s moss and leaves easily block terminations.
- •Keep the termination clear and install critter guards where necessary.
- •Run the drain into a condensate pump if elevation changes make gravity draining unreliable.
Prevent the Next Clog
Call Us If You Notice:
AC shuts off and thermostat displays a float switch or water error.
Water leaking from the furnace cabinet or ceiling vents.
Musty odors or visible mold around registers.
Condensate pump running continuously or making unusual noises.
AC Drain Line FAQ
Keep Water Where It Belongs — Outside Your HVAC System
Efficiency Heating & Cooling’s drain cleaning and prevention services keep your system safe, efficient, and mold free. Call now to protect your home before summer humidity hits full force.