This is the failure-mode companion to our main AC repair service. A water leak is one of the few AC problems that does collateral damage to your home while you wait, so it is worth understanding and acting on quickly.
First step: shut it off
Turn the AC off at the thermostat. That stops the coil from producing more condensate, and if the hidden cause is a frozen evaporator coil, it lets the ice thaw. Soak up standing water away from drywall and flooring, then call. Running a leaking system just adds water to the damage.
Why an AC leaks water — the causes in order
- Clogged condensate drain line — the cause about 70% of the time. Algae and dust plug the 3/4-inch PVC line and water backs up over the pan. Clearing: $145–$245.
- Failed condensate pump — on attic, closet, and basement units that pump water uphill. A stuck float or dead pump overflows the reservoir.
- Frozen evaporator coil melting — ice from an airflow or refrigerant problem melts faster than the drain can carry it. See frozen evaporator coil.
- Rusted or cracked drain pan — on older units the metal pan corrodes through.
- Disconnected or sloped-wrong drain line — often after a prior poor install.
The clog and the freeze are linked to two things many homeowners control: filter changes and yearly maintenance. A clogged AC drain line guide and our filter replacement guide cover the prevention side.
The dirty-filter-to-leak chain
A surprising number of water leaks trace back to a $30 filter. A clogged filter starves airflow across the evaporator coil, the coil freezes, and when it melts — often right after you shut the system off — it dumps more water than the pan and line can handle. So a water leak can really be a frozen-coil problem, which is really a filter or refrigerant problem. That is why the first things we check on a leak are the filter and whether the coil has been icing, not just the drain.
Why drain lines clog in SoCal
The condensate line is dark, damp, and fed a steady diet of dust and organic matter — ideal for algae and slime. It is worse in humid coastal zones like Santa Monica and Long Beach and during the muggy late-summer stretch across the basin. Homes with weak filtration clog faster. The cure is partly maintenance behavior: a yearly drain flush at your spring tune-up, a clean filter, and sometimes a float safety switch that shuts the AC off before an overflow ever reaches the ceiling.
AC water leak repair pricing
| Repair | Typical cost |
| Diagnostic (waived with repair) | $89 / $149 after-hours |
| Condensate drain line clearing | $145–$245 |
| Condensate pump replacement | quoted per unit |
| Drain pan / float-switch work | quoted with diagnosis |
| Evaporator coil cleaning (if freezing) | $385–$685 |
Every major brand
Condensate leaks happen on every brand — the drain, pan, and pump are universal. Brand-specific cooling diagnostics: Carrier, Trane, Lennox, Rheem, Goodman, and York AC not cooling.
Frequently asked questions
Why is my AC leaking water inside the house? +
The most common cause by far is a clogged condensate drain line. Your evaporator coil pulls 5–20 gallons of water out of the air on a hot LA day, and that water drains out through a 3/4-inch PVC line. Algae and dust build up inside the line, it backs up, and water overflows the drain pan onto the ceiling or floor. Other causes: a failed condensate pump (on systems that pump uphill), a cracked or rusted drain pan, a frozen evaporator coil that melts all at once, or a disconnected drain line. Clearing a clogged line runs $145–$245 and takes about 30 minutes.
Is an AC water leak an emergency? +
It is not dangerous like a gas or electrical fault, but it can do expensive damage fast, so do not ignore it. Standing water against drywall, ceilings, and flooring causes staining, warping, and mold within days. The immediate move: turn the AC off at the thermostat to stop producing more condensate, soak up standing water, and call. Turning it off also lets a frozen coil (a common hidden cause) thaw. We clear the drain, find why it clogged, and check the pan and pump. Catching it early is the difference between a $200 drain clearing and a drywall repair.
Can I clear a clogged AC drain line myself? +
You can try the first step: many homes have a capped access tee near the indoor unit, and a wet/dry vacuum at the outdoor drain termination can pull the clog. Some homeowners also pour a cup of distilled vinegar into the access port every few months as prevention. Where it gets beyond DIY is a clog that will not clear, a line that re-clogs quickly, a failed condensate pump, or a rusted pan — those need a tech. And if the real cause is a frozen coil or a refrigerant problem, clearing the drain only treats the symptom. We find the actual cause rather than just mopping up.
What does it cost to fix an AC that is leaking water? +
It depends on the cause, and our $89 diagnostic ($149 after-hours) credits to the repair. A clogged condensate drain line clearing runs $145–$245. A condensate pump replacement is a separate part on systems that need to pump water uphill to a drain. A rusted or cracked drain pan, a disconnected line, or a frozen-coil cause each carry their own fix. If the leak traces to a frozen evaporator coil, the underlying issue is usually airflow or refrigerant and we price that accordingly. We confirm the cause before quoting, not after.
Why does my AC drain line keep clogging? +
Because the drain line is the perfect environment for biological growth — dark, damp, and full of the dust and organic matter the coil washes down. Algae and slime build into a plug. In Southern California this is worse in humid coastal zones and during the muggy late-summer stretch. Homes with poor filtration feed more dust into the system and clog faster. The fix is partly behavior: a yearly drain flush during your spring tune-up, a clean filter, and sometimes adding an access port or a float switch that shuts the AC off before an overflow reaches the ceiling.
What is a condensate pump and do I need one? +
A condensate pump is a small electric pump used when the indoor unit sits below the drain exit — common with attic, closet, and basement air handlers where water cannot drain by gravity. It collects condensate in a small reservoir and pumps it up and out. When the pump fails or its float switch sticks, the reservoir overflows and you get a leak directly under the unit. Not every system has one; gravity-drained units do not. If yours has a pump and it failed, replacing it resolves the leak. We confirm whether your setup uses a pump during the diagnostic.
Can a dirty air filter cause my AC to leak water? +
Indirectly, yes, and it is a common chain we see. A clogged filter restricts airflow across the evaporator coil, the coil gets too cold and freezes, and when the ice melts — especially after you shut the system off — it dumps more water than the drain pan and line can handle, causing an overflow. So a $30 neglected filter can present as a water leak. The first thing we check on a leaking system is the filter and whether the coil has been freezing. Replacing the filter and addressing the freeze prevents the recurring leak.
