AC troubleshooting guide · Las Vegas
AC leaking water? Clogged drain lines and what to do first
Short answer: if your AC is leaking water, start here: an air conditioner pulls moisture out of the air, and that water is supposed to flow away through a condensate drain line. When an AC leaks water inside the house, the cause is most often a clogged drain line, a cracked or overflowing drain pan, or an indoor coil that froze and is now melting. Turn the system off, dry the area quickly, and have the drain cleared by a licensed contractor.
A little water outside the house while the AC runs is normal. Water inside, on a ceiling, around the indoor unit in a closet or garage, or in the attic is not. This guide explains where the water comes from, the signs of a clogged AC drain line, the safe first steps, and what to ask the contractor.
1. Where the water comes from
The indoor coil (the evaporator) does two jobs: it removes heat and it removes humidity from the air, as the Department of Energy explains (energy.gov). The moisture condenses on the cold coil, drips into a drain pan and leaves the house through the condensate drain line. As long as that path is open, you never see the water.
ENERGY STAR includes checking and inspecting the condensate drain in a typical maintenance visit, and warns that a plugged drain can cause water damage in the house and affect indoor humidity levels (ENERGY STAR). The EPA recommends keeping air conditioning drip pans clean and the drain lines unobstructed and flowing properly (EPA).
2. Common causes of an AC leaking water
- Clogged condensate drain line: dust and debris can build up and block the line. The water backs up into the pan and overflows.
- Cracked, rusted or misaligned drain pan: water escapes before it reaches the drain.
- A frozen indoor coil that is melting: when ice on the coil thaws, it can release more water than the pan handles. See our guide to an AC freezing up.
- A disconnected or damaged drain pipe: a joint can come loose, especially in a hot attic or garage.
- A clogged filter: by restricting airflow, it can lead to a frozen coil, which then leaks as it melts.
3. Signs your AC drain line is clogged
- Standing water in the drain pan under the indoor unit.
- Water on the floor around the indoor unit, or a stain or drip on the ceiling below an attic unit.
- Water dripping from a pipe that is normally dry. Under the residential code (IRC M1411.3.1), many systems have a secondary drain or an auxiliary pan whose drain must discharge to a conspicuous point so occupants notice when the primary drain is stopped (Department of Energy inspection checklist). If that pipe is dripping, treat it as a warning.
- The AC shut itself off. The same code section allows a water-level detection device that shuts off the equipment when the primary drain is blocked. A system that suddenly stops, with water in the pan, may have tripped it. Our AC not turning on guide covers the other causes.
- A musty smell near the indoor unit or higher humidity indoors.
4. What you can safely do first
- Turn the system off at the thermostat. This stops new water from forming on the coil. If water is near the unit's electrical parts, an outlet or a light fixture, also turn it off at the breaker.
- Protect the area. Put towels or a bucket under the drip and move belongings away. If water is coming through a ceiling, keep people away from the spot below it.
- Dry quickly. The EPA advises acting quickly when water leaks indoors: if wet materials are dried within 24 to 48 hours, in most cases mold will not grow.
- Look, don't take apart. If the drain pan is visible without removing panels, check whether it holds water. You can also look outside for a secondary drain that is dripping. Take photos for the contractor.
- Check the filter. If it is clogged, replace it. It is a common contributor to a frozen, then leaking, coil.
What not to do: do not pour strong chemicals or drain cleaners into the line, do not remove panels from the indoor unit, and do not keep running the system while water is overflowing. Do not try to bypass or disconnect a safety switch that shut the system off: it is doing its job.
5. Las Vegas: why drains clog and leaks go unnoticed
Dry air does not mean your AC makes no water. In July and August, the National Weather Service climate summary for Las Vegas notes that monsoon moisture brings higher than average humidity to the valley. More humidity in the air means more water for the coil to remove, and more water running through a drain line that may already be partly blocked.
The same NWS summary describes the blowing dust and sand that come with strong winds in the valley. Dust that gets past a dirty filter can collect on the coil and in the pan. And because many Las Vegas homes have the indoor unit in an attic or garage, a slow overflow can go unseen until a ceiling stain appears. A drain check at the start of each cooling season is a good habit.
6. When to call a licensed AC contractor
- Water is leaking into a ceiling, wall or floor.
- The drain pan is full, or the secondary drain is dripping.
- The system shut itself off and there is water in the pan.
- You see ice on the coil or refrigerant lines.
- The leak comes back after you replaced the filter and dried the area.
Ask the contractor to clear the line, check the pan, the drain slope and any safety switch, and explain what caused the clog. If the coil froze, ask them to find out why. If refrigerant work is needed, it must be done by an EPA 608-certified technician (EPA).
In Nevada, air conditioning repair is contractor work, and the exemption for jobs under $1,000 does not apply to air conditioning work (NRS 624.031). Verify the license in the free Nevada State Contractors Board license search. If the water damaged drywall or flooring, you may also need someone with experience in water damage and mold cleanup.
ClimaVegas does not perform air conditioning work. We connect you with independent air conditioning contractors in the Las Vegas area.
Call to be connected with a local AC contractor
7. More guides for Las Vegas homeowners
- AC not cooling or blowing warm air: a homeowner's checklist.
- AC not turning on: thermostat, breakers and a compressor that won't start.
- AC freezing up: why ice forms and how to thaw it safely.
- Emergency AC guide: first checks and heat safety.
- AC repair in Las Vegas: the common repairs, explained.
- AC repair in Henderson: city permits and HOA rules.
- HVAC guide for Las Vegas: efficiency rules, maintenance and permits.
- Heating repair guide: furnaces, heat pumps and carbon monoxide safety.
Frequently asked questions
Why is my AC leaking water inside the house?
An air conditioner removes moisture from the air, and that water is supposed to drain away through a condensate line. Most indoor leaks happen when that drain line is clogged, the drain pan is cracked or overflowing, or the indoor coil froze and the ice is melting faster than the drain can handle.
How do I know if my AC drain line is clogged?
Common signs are standing water in the drain pan under the indoor unit, water around the unit or on the ceiling below it, water dripping from a secondary drain pipe that normally stays dry, or a system that shut itself off because a water-level safety switch tripped.
Is water dripping from a pipe outside my house normal?
It depends on which pipe. The primary condensate drain carries water away while the AC runs. Where an overflow could damage the building, codes require a secondary drain to discharge to a conspicuous place so occupants notice when the primary drain is stopped. If water is coming from a pipe that is normally dry, often one placed where you will see it, the primary drain is likely clogged.
What should I do first if my AC is leaking?
Turn the system off at the thermostat, and if water is near electrical parts or outlets, turn it off at the breaker too. Soak up the water and dry wet materials quickly; the EPA says drying within 24 to 48 hours usually prevents mold growth. Then call a licensed AC contractor to clear the drain and find the cause.
Can I use chemicals to clear my AC drain line?
Avoid strong chemicals and drain cleaners. A clog is often only part of the problem, and clearing the line safely is a job for a contractor. Let a contractor clear the line and check the pan, coil and safety switch.