Why Is My AC Leaking Water? Complete Portland Troubleshooting Guide
7 common causes of AC water leaks with step-by-step fixes. Learn when it's normal drainage vs emergency repair.
Serving Portland, Beaverton, Lake Oswego, West Linn, and the greater metro area since 2008.
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🚰 Quick Diagnosis: Is Your AC Leak Normal or Emergency?
✅ Normal Water Drainage:
- • Small amount outside near outdoor unit
- • 5-20 gallons per day during cooling
- • Clear water from condensate drain
- • No water damage or staining
- • AC operating normally otherwise
🚨 Emergency - Call Professional:
- • Water leaking inside the house
- • Pooling water around indoor unit
- • Water stains on ceiling/walls
- • Musty or moldy smell
- • AC not cooling or making ice
Portland homes: Dry climate means less condensate, so leaks often signal real problems rather than normal operation.
Understanding AC Water Leaks in Portland Homes
AC units produce water as a normal part of cooling—humidity from your home condenses on the cold evaporator coil and drains away. But when this process goes wrong, water can leak where it shouldn't, causing damage to your home and indicating bigger problems with your system.
After 17 years diagnosing AC issues in Portland, I've found that most "leaks" are actually normal drainage misunderstood by homeowners. However, real leaks require immediate attention to prevent mold, water damage, and poor indoor air quality. Portland's dry climate actually makes leaks more concerning because we have less humidity than coastal areas, so when leaks occur, they're usually symptoms of maintenance issues rather than normal operation.
This guide covers the 7 most common causes of AC water issues, with clear steps for what you can fix yourself and when to call our professional technicians. Each section includes Portland-specific context and cost estimates for repairs.
7 Common Causes of AC Water Leaks (In Order of Likelihood)
1. Clogged Condensate Drain Line (80% of Cases)
Why It Happens
Your AC produces condensate (water) that drains through a PVC pipe. Over time, algae, mold, dust, and mineral deposits clog this drain. When clogged, water backs up and overflows the drain pan, leaking into your home. This is the #1 cause of AC water leaks.
Symptoms
- • Water leaking from indoor unit
- • Water stains on ceiling below unit
- • Musty or moldy smell
- • AC may shut off automatically
- • Gurgling sounds from drain
DIY Solution
- Turn AC off at thermostat
- Locate drain line (usually exits near outdoor unit)
- Use shop vac to suck out clog from outdoor end
- Pour 1 cup white vinegar down drain to kill algae
- Flush with water and restart AC
Cost & Prevention
$0-50 for vinegar/shop vac. Prevent with monthly vinegar flush during cooling season.
Portland Context
Our dry climate means less water production, but mineral content in water can still cause buildup. Change filters monthly to reduce dust in drain.
2. Frozen Evaporator Coil Thawing
Why It Leaks
When the evaporator coil freezes (from dirty filter, low airflow, or low refrigerant), ice forms on the coil and drain pan. As it thaws, the sudden rush of water overwhelms the drain system, causing overflow and leaks.
Symptoms
- • Ice on indoor unit followed by water leak
- • AC cycles on/off frequently
- • Reduced cooling capacity
- • Water leak occurs intermittently
Fix the Root Cause
Don't just deal with the leak—fix why it's freezing. See our AC Freezing guide for complete solutions.
Immediate Action
- • Turn AC off until coil thaws (6-12 hours)
- • Switch to fan-only to help thaw
- • Check and replace air filter
- • Ensure all vents are open
Cost
$100-300 diagnostic + underlying issue repair
3. Cracked or Rusted Drain Pan
Why It Happens
The plastic drain pan under your indoor unit collects condensate. Over time (10+ years), it can crack from age, develop rust holes, or warp from heat. When damaged, water leaks through the cracks instead of draining properly.
Symptoms
- • Water dripping from ceiling below unit
- • Water damage to ceiling drywall
- • Visible cracks or rust on drain pan
- • Water pooling on floor under unit
Temporary vs Permanent Fix
Temporary (DIY)
Place bucket under leak, seal crack with epoxy. Good for 1-2 weeks while scheduling repair.
Permanent (Professional)
Replace entire drain pan assembly. Requires disassembling indoor unit.
Cost
$150-300 professional replacement
Additional Causes of AC Water Leaks
The remaining 4 causes with key details:
4. Improper Installation
Drain line not sloped properly, causing backup. Common in DIY installations. Professional re-slope: $100-250.
5. Disconnected Drain Line
Vibration loosens fittings over time. Easy DIY reconnect, but call pro if unsure. Cost: $100-200.
6. Failed Drain Pump
Some systems need pump for basement units. Pump replacement: $150-300. Check if your system has one.
7. Low Refrigerant
Causes coil freeze, then thaw overflow. EPA-certified repair only. Cost: $200-500 leak detection + recharge.
Step-by-Step AC Leak Troubleshooting
Assess the Situation
Is water leaking inside the house or just outside? Indoor leaks = emergency. Outdoor drainage may be normal.
Turn AC Off & Contain Water
Shut off system, place towels/bucket under leak to prevent further damage.
Check Drain Pan & Coil
Look for ice, cracks, or standing water. If frozen, let thaw 6-12 hours.
Clear the Drain Line
Find outdoor drain exit, use shop vac to suck out clogs, flush with vinegar.
Test & Monitor
Restart AC, watch for 30 minutes. If leak returns, call professional.
🚨 When to Call Professional Immediately:
- • Water leaking inside your home
- • Ceiling stains or water damage
- • Mold or musty smell
- • AC making ice or not cooling
- • Can't locate or access drain line
- • Leak persists after DIY attempts
Preventing AC Water Leaks in Portland
Monthly Maintenance
- • Check drain pan for standing water
- • Pour 1 cup vinegar down drain monthly
- • Change air filters to reduce dust in drain
- • Inspect drain line for kinks or damage
- • Clean area around outdoor drain exit
Professional Service
- • Annual drain line cleaning and inspection
- • Refrigerant level check
- • Drain pan inspection for cracks
- • Ductwork inspection for leaks
- • Full system efficiency test
Portland-Specific Prevention
- • Our mineral-rich water causes faster drain buildup - monthly vinegar flushes essential
- • Dry climate means less condensate, so leaks are more likely real problems
- • Older Portland homes (pre-1980) often have inadequate or missing drain lines
- • Crawlspace installations common - check for sagging or kinked drain lines
- • Heat waves increase water production - monitor drains during 90°F+ weather
Frequently Asked Questions About AC Water Leaks
Yes, some water drainage outside is normal (5-20 gallons/day) during cooling operation. This is condensate from humidity in your home. But indoor leaks or pooling water indicate problems like clogged drains, frozen coils, or improper installation that need immediate attention.
Turn off AC, locate drain line (usually PVC pipe exiting near outdoor unit), use shop vac to suck out clog from outdoor end, pour vinegar down drain to kill algae. If that fails, call professional. Never pour drain cleaners - can damage AC components.
Indoor leaks mean drain pan overflow or cracked pan. Most common: clogged condensate drain line (80% of cases). Can cause ceiling damage if not fixed quickly. Turn off AC immediately and call professional if water is leaking inside.
5-20 gallons per day normal in Portland's climate during cooling season. More indicates high humidity or system issues. Less than 1 gallon/day might mean drain problems or low airflow. Track with bucket test if concerned.
Yes! Clogged drains lead to overflow, water damage, mold growth, poor indoor air quality, and can force system shutdown to prevent damage. Many systems have safety switches that turn off AC when drain clogs to prevent flooding your home.
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