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AC Leaking Water

Why is my AC Leaking Water

Why Is My AC Leaking Water? 7 Common Causes & How to Fix  If you’ve noticed your AC leaking water, pooling around the air handler, or water stains forming near your vents, you’re not alone. An air conditioner leaking water is one of the most common HVAC problems homeowners in Cupertino, CA experience—especially during hot, dry summers when units run nonstop.
The good news? Most causes are completely fixable. In this guide, we’ll break down the top reasons your AC is leaking water, how serious the problem is, when you can troubleshoot it yourself, and when you should call an HVAC technician.

Is It Normal for an AC to Leak Water?Your air conditioner naturally removes moisture from the air. That moisture normally drains through a condensate drain line and into your home’s plumbing or outdoors.
It is not normal for water to leak from the AC unit itself, pour from vents, or drip around the indoor handler. Any visible leaking means something is wrong with the drainage process.

1. Clogged Condensate Drain LineThe #1 reason an AC leaks water is a blocked drain line. Over time, dust, algae, mold, and debris build up inside the drain pipe and prevent water from flowing out.
Signs of a clogged drain line:

• Standing water in the drain pan
  
• Water dripping from the indoor AC unit
  
• Musty or moldy smell
  
• AC shuts off unexpectedly
  

How to fix it:A wet/dry vacuum can sometimes unclog the drain line. But if the blockage is deep or caused by algae growth, you’ll need a professional to flush the system and treat it to prevent future buildup.

2. Dirty or Blocked Air FilterA dirty AC filter restricts airflow, causing the evaporator coil to freeze. When the ice melts, the drain pan can overflow, leading to water leakage.
Warning signs:

• AC not cooling well
  
• Weak airflow from vents
  
• Ice forming on the refrigerant lines
  

Fix:Replace your air filter every 30–60 days during summer in the Cupertino area, where AC units run frequently.

3. Low Refrigerant Causing Coil FreezingRefrigerant leaks lower pressure in the system and cause the coil to freeze. When that ice melts, water spills over the drain pan.
Look for these symptoms:

• Hissing or bubbling noise from AC
  
• AC running longer than usual
  
• Warm air coming from vents
  
• Higher than normal energy bills
  

Important:You cannot fix this yourself. Refrigerant leaks require EPA-licensed HVAC technicians to repair the leak, recharge refrigerant, and test system performance.

4. Damaged or Cracked Drain PanYour AC’s drain pan catches condensation. Over years of use, especially in older Cupertino homes, pans often rust, crack, or become misaligned.
What to look for:

• Water dripping directly from the bottom of the indoor unit
  
• Visible rust around the pan
  
• Water damage on ceiling or walls
  

A cracked drain pan must be replaced—repairs rarely hold.

5. Disconnected Drain LineSometimes the drain pipe loosens or disconnects at the drain pan, especially if the unit was recently serviced or poorly installed.
Symptoms:

• Water leaking immediately when AC turns on
  
• No water exiting the normal drain location
  

This is a quick fix for an HVAC technician, but continuing to run the AC can cause indoor water damage.

6. Frozen Evaporator Coil from Poor AirflowBesides dirty filters, airflow can be restricted by:

• Dirty evaporator coils
  
• Blocked return grilles
  
• Closed supply vents
  
• Malfunctioning blower motor
  

When airflow drops, the coil gets too cold and freezes. Once the ice melts, water spills over the edges of the drain pan.

7. Improper AC InstallationIf your AC was installed incorrectly, water may not drain properly.
Common installation mistakes:

• Unit not level
  
• Incorrect drain line slope
  
• Improperly sized system (undersized or oversized)
  
• Wrong plenum or duct configuration
  

Improper installation is a major cause of AC water leaks in newer Cupertino homes and remodels.

Is It Safe to Keep Running an AC That’s Leaking Water?No. A leaking AC can lead to:

• Ceiling or drywall damage
  
• Mold growth
  
• Electrical hazards
  
• Complete system failure
  

Shut off your air conditioner and call a licensed technician if the leak is severe or persistent.

When You Can Fix It Yourself vs. When to Call a Pro✔ DIY Fixes You Can Try:

• Replace the air filter
  
• Check for ice on the coil and let it thaw
  
• Ensure vents aren’t blocked
  
• Make sure the unit is level
  
• Use a wet/dry vacuum to clear the drain line (if accessible)
  

✖ Call an HVAC technician if:

• The drain line keeps clogging
  
• You see a refrigerant leak
  
• The evaporator coil is frozen repeatedly
  
• Water is leaking from the ceiling or walls
  
• You suspect improper installation
  

Water leaks are usually easy to stop once the root cause is found—but delaying professional repair can lead to expensive damage.

How We Fix AC Leaks in Cupertino, CAAt HVAC Cupertino, our technicians specialize in diagnosing and repairing all causes of AC water leaks, from simple drain clogs to full system repairs.
Our AC leak repair service includes:

• Full system inspection
  
• Clearing or replacing the condensate drain line
  
• Repairing or replacing the drain pan
  
• Checking refrigerant levels
  
• Inspecting the evaporator coil
  
• Verifying system installation and tilt
  
• Preventative maintenance to stop future leaks
  

We handle issues quickly—often the same day—so you can stay cool without risking water damage to your home.

Prevent AC Water Leaks With Regular MaintenanceThe best way to avoid AC water leaks is yearly professional maintenance. During a tune-up, we:

• Clean the condenser and evaporator coils
  
• Flush the drain line
  
• Check for refrigerant leaks
  
• Inspect the blower motor
  
• Ensure the system drains properly
  

A small investment in maintenance often prevents hundreds or even thousands in water damage repairs.

Need Fast AC Leak Repair in Cupertino? We’re Here to Help.If your AC is leaking water inside your home, don’t wait—water damage spreads fast.
👉 Call HVAC Cupertino today for fast, affordable AC leak diagnosis and repair.
We proudly serve Cupertino, San Jose, Sunnyvale, Santa Clara, and surrounding areas.
📞 (408) 740-7079
🌐 www.hvaccupertino.com
Stay cool. Stay safe. Let us fix your AC leak today.