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How to fix an AC condensate leak

We'll help you find and fix the condensate leak—clog, pan, slope, or pump—or know when to call an HVAC technician.

Troubleshooting · Home plumbing
30–60 min
What you'll need
  • Wet/dry vacuum (for clearing drain)
  • Bleach or vinegar (for drain flush)
  • Replacement drain pan (if cracked and accessible)
Step 1 of 9

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Quick triage — pick your path

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Steps

Goal: Confirm the leak is condensate, locate the cause, and fix the drain—or call an HVAC technician.

Confirm condensate

Goal: Verify the leak is condensate (clear water), not refrigerant.

  • Condensate is clear water from humidity on the evaporator coil. Refrigerant leaks show oily residue and often a hissing sound.
  • Check where the water appears: under the indoor unit, at the drain line outlet, or dripping from the ceiling.
  • Good: Clear water—condensate leak. Proceed to Shut off AC.
  • Bad: Oily or hissing—refrigerant. Call an HVAC technician. Do not attempt refrigerant repair.

Shut off AC

Goal: Work safely with the unit off.

  • Turn off the thermostat and circuit breaker. Confirm the unit is off.
  • Good: No fan or compressor operation. Proceed to Locate drain.
  • Bad: Unsure which breaker—turn off the main AC breaker.

Locate drain

Goal: Find the condensate drain path and drain pan.

Clear drain

Goal: Clear a clogged condensate drain.

  • Use a wet/dry vacuum on the drain line outlet to pull the clog—seal the vacuum hose to the pipe for best suction. Or pour a cup of bleach or vinegar into the drain line access and flush with water.
  • Good: Drain flows freely. Proceed to Verification.
  • Bad: Drain is still clogged—try a drain snake or call an HVAC technician.

Drain pan

Goal: Fix or replace a cracked or overflowing drain pan.

  • Inspect the drain pan for cracks. Replace if cracked. If overflowing, clear the drain and check the slope. Confirm the pan is intact.
  • Good: Pan is intact and drain is clear. Proceed to Verification.
  • Bad: Pan is cracked and not accessible—call an HVAC technician.

Condensate pump

Goal: Check that the condensate pump runs and the discharge line is clear.

  • If you have a condensate pump, confirm it runs when the AC runs. Check the discharge hose for kinks or clogs.
  • Good: Pump runs and water flows out. Proceed to Verification.
  • Bad: Pump failed or discharge blocked—replace the pump or call an HVAC technician.

When to get help

Call an HVAC technician if:

  • The leak is refrigerant (oily residue, hissing sound).
  • The evaporator coil is frozen.
  • The drain or pan is inside the wall and inaccessible.
  • The condensate pump has failed and you cannot replace it.
  • You are not comfortable with the repair.

Do not attempt to repair refrigerant leaks. The technician must be EPA-certified.

Verification

  • Condensate drain flows freely when the AC runs.
  • No water pooling in the drain pan.
  • No drips from the unit or at the drain line connection.
  • AC operates normally without leaking.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Confirm condensate vs refrigerant Verify the leak is clear water (condensate), not refrigerant. Refrigerant = call a pro.
  2. Clear the drain Use a wet/dry vacuum or bleach flush to clear a clogged condensate drain.
  3. Check drain pan and slope Inspect the drain pan for cracks; check that the drain line slopes downhill.
  4. Check condensate pump If you have a pump, confirm it runs and the discharge line is clear.
  5. Call an HVAC technician Refrigerant leak, frozen coil, inaccessible drain, or failed pump you cannot replace.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Where the water appears (under unit, at drain outlet, ceiling)
  • Whether the leak is clear water (condensate) or oily (refrigerant)
  • Whether the drain line is clogged
  • Whether the drain pan is cracked
  • Whether a condensate pump is present and running
  • Steps already tried

Is the leak clear water (condensate) or oily with a hissing sound (refrigerant)?

Condensate is clear water from humidity. Refrigerant leaks show oily residue and often hissing—call an HVAC technician immediately.

Check where the water appears. Condensate is clear water. Refrigerant shows oily residue and may hiss. Good: clear water—condensate leak. Bad: oily or hissing—refrigerant; call an HVAC technician. Do not attempt refrigerant repair.

Condensate Refrigerant

You can change your answer later.

Can you access the condensate drain and drain pan?

Shut off the AC at the thermostat and circuit breaker first. Trace the PVC drain from the indoor unit. The drain pan is under the evaporator coil.

Turn off the thermostat and circuit breaker. Find the condensate drain and drain pan. Trace from the indoor unit to the exit. Good: you can access them. Bad: drain is inside the wall—call an HVAC technician.

Yes No

You can change your answer later.

Is the condensate drain clogged?

Water backing up at the pan or drain connection suggests a clog. Algae and mold often block the line.

Use a wet/dry vacuum on the drain outlet to pull the clog. Or pour bleach or vinegar into the drain access and flush with water. Good: drain flows freely. Bad: still clogged—try a drain snake or call an HVAC technician.

Yes (cleared) No (still clogged or not the cause)

You can change your answer later.

Is the drain pan cracked or overflowing?

A cracked pan leaks. An overflowing pan usually means the drain is clogged or the slope is wrong.

Inspect the drain pan for cracks. Replace if cracked. If overflowing, clear the drain and check the slope. Good: pan intact and drain clear. Bad: pan cracked and not accessible—call an HVAC technician.
Question

Is the drain pan the problem?

Continue

You can change your answer later.

Does the drain line slope downhill?

The drain must drop at least 1/4 inch per foot. Flat or uphill sections cause backup.

Check that the condensate drain slopes toward the exit. Reposition if needed. Good: slope is correct. Bad: cannot fix slope—call an HVAC technician.

Yes No

You can change your answer later.

Do you have a condensate pump?

Some ACs use a pump when gravity drainage is not possible. The pump can fail or the discharge can clog.

If you have a condensate pump, confirm it runs when the AC runs. Check the discharge hose for kinks or clogs. Good: pump runs and water flows. Bad: pump failed or discharge blocked—replace pump or call an HVAC technician.

Yes (have pump, it works) No pump or pump failed

You can change your answer later.

Is the drain line connection loose or leaking?

The fitting where the drain connects to the pan can loosen or crack.

Check the connection at the drain pan. Tighten or replace the fitting. Good: connection is secure. Bad: still leaking—call an HVAC technician.

Yes No

You can change your answer later.

Leak is fixed

Condensate drains freely. No water pooling in the pan. Run the AC for 30 minutes and confirm no drips. Install an overflow switch if your unit does not have one—it shuts off the AC when the pan fills.

Done

Call an HVAC technician

Call an HVAC technician if: the leak is refrigerant (oily, hissing); the evaporator coil is frozen; the drain or pan is inaccessible; or the condensate pump has failed and you cannot replace it. Do not attempt refrigerant repairs. The technician must be EPA-certified.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Where does AC condensate usually leak?
Common spots: the condensate drain line (clogged with algae or mold), the drain pan (cracked or overflowing), the drain line connection, and the condensate pump discharge. A flat or uphill drain line can also cause backup.
Can I fix an AC condensate leak myself?
Yes, for drain clogs, drain pan replacement when accessible, and slope issues. Clear the drain with a vacuum or bleach flush. Replace a cracked pan if you can reach it. Condensate pump failures may need a pro if the pump is hard to access.
When should I call an HVAC technician for an AC condensate leak?
Call an HVAC technician if the leak is refrigerant (oily, hissing), the evaporator coil is frozen, the drain is inside the wall and inaccessible, or the condensate pump has failed and you cannot replace it.

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