Water leaking from an AC unit gets your attention fast. It might be a puddle next to the indoor unit or a damp patch on the wall. Whatever it looks like, you want to know two things. What’s causing it, and does it need AC repair?
We get this call often during summer. The good news is that the reason is usually simple. Sometimes you can fix it in ten minutes. Times you need a professional. Here’s how to find out which one you are dealing with.
Why Does an AC Even Make Water?
Your AC does more than cool the air. It also takes moisture out of it. Warm air from your home blows over the evaporator coil, which’s very cold. The moisture becomes water on the coil to a cold glass of water on a hot day.
This water is supposed to drip into a pan and flow out through a drain line. You never see it. That is the way it should be. When the line is blocked, the pan breaks or the coil freezes the water has no place to go. So it ends up inside your house.
What to know: A little water outside is normal. Ductless mini splits drip from a hose and central systems have a drain pipe that ends near the house. Water inside is the issue.
Main Reasons for Water Leaking From an AC Unit
Here is an overview of the usual reasons. We will go through them one by one.
| Reason | What You Usually See | Fix Difficulty |
|---|---|---|
| Blocked drain line | Water near the indoor unit or a ceiling stain | Easy to medium |
| Dirty air filter | Ice on the coil then water when it melts | Easy |
| Frozen evaporator coil | Ice on the pipes weak airflow | Medium |
| Low refrigerant | Ice hissing sound warm air | Needs a technician |
| Cracked drain pan | Water under the unit with a clear drain | Needs a technician |
| Damaged pipe insulation | Wet pipes, drips along the line | Medium |
| Unlevel unit | Water spilling off one side | Needs a technician |
A Clogged Drain Line Is the Most Common Problem
If your AC is water inside the house start here. Dust, algae and slime build up in the drain line over time. It is dark and wet in there. Stuff grows. The opening gets smaller and smaller until water can’t get out.
Then the drain pan fills up. Spills over. In Los Angeles homes the air handler is in the attic or a closet. So you might not see the leak away. You just notice a stained ceiling a days later. Many systems also have a switch that turns the AC off when the pan is full. If your AC stopped working for no reason and there is water nearby check the drain first.
Tip: Go outside on a day while the AC is running and find the end of the drain pipe. If nothing drips out after an hour or so the line might be blocked.
Dirty Filters and Frozen Coils
A dirty filter is simple. It causes a lot of leaks. When the filter is clogged less air moves across the coil. The coil gets cold and ice starts to form. You might see frost on the copper pipes near the unit. The house also won’t cool well and that is often the first sign.
The water appears later. When the AC turns off the ice. A lot of water drips at once. The pan can’t handle it. Overflows. So sometimes the puddle is just melted ice. Changing the filter fixes it in cases. If your vents are also blowing weakly our post on AC blowing air goes over the other reasons.
Signs your coil may be frozen
- Ice on the indoor pipes or coil
- Weak airflow from the vents
- The house isn’t cooling like it used to
- Water pooling after the AC has been off for a while
Reasons Your AC Might Be Leaking
These happen less often but we do see them.
- Low refrigerant: Low refrigerant causes pressure to drop. The coil gets colder than it should. It freezes, thaws and leaks. You can’t fix this one yourself. A licensed professional has to find the leak and recharge the system.
- Cracked or rusty drain pan: Older units can rust through. The water drips out when the drain line is clear.
- Worn pipe insulation: Warm air touches the refrigerant line and water forms on the outside. It looks like a leak. It is really condensation. New HVAC insulation usually fixes it.
- Poor installation: If the indoor unit is not level water runs to one side and spills. We see this more with rushed installations.
- Humid days: Near the coast the air holds moisture. Your AC collects water on those days and a half-blocked line can’t keep up.
Safety note: Water and wiring don't mix. If you see water near parts turn the power off at the breaker before you touch anything.
What To Do When You Find Water
Here is the order we would follow.
- Turn the AC off: Use the thermostat. If there is a lot of water switch it off at the breaker too.
- Dry everything: Use a towel to clean the water. Wet drywall and flooring can grow mold quickly.
- Check the filter: If it is gray and clogged replace it. Our AC filter replacement explains how often it should be done.
- Look at the drain line: Find the outlet. See if anything is stuck in it.
- Clear a clog: A /dry vacuum on the outdoor end of the drain pipe can pull the gunk out. Only do this if you can reach it safely.
- Thaw the coil: If you see ice leave the AC off for a hours. Running only the fan helps it melt faster.
- Turn it on and watch: If the water comes back. Get it checked.
What Not To Do
Some fixes can make things worse.
- Don’t keep running the AC while it leaks.
- Don’t pour chemicals down the drain line. Plain white vinegar is safer for a cleaning.
- Don’t try to add refrigerant on your own.
- Don’t use sharp tools in the unit. The coil is easy to damage.
- Don’t ignore a drip. It rarely stays small.
When Its Time To Call a Professional
Say you changed the filter and checked the drain and the water still comes back. Then the problem is probably more serious. It could be low refrigerant, a rusted pan or something wrong with the coil. These are hard to see without the tools.
Call sooner if there is a lot of water a musty smell or the breaker keeps tripping. A ceiling stain means the leak has been going on for a while. An AC system diagnostic on costs a lot less than fixing a damaged ceiling or floor.
How To Prevent It From Happening
Most leaks can be avoided with a few simple habits.
- Check the filter every month. Replace it every one to three months.
- Have the drain line flushed once or twice a year.
- Keep the area around the unit clear.
- Make sure the unit is level.
- Schedule summer maintenance before the months when the AC works the hardest.
Tip: Set a filter reminder on your phone. It takes two minutes. Saves a lot of headaches.
Fix the Drip Now Save Your Ceiling Later
Most AC leaks aren’t an emergency. A clogged drain, a dirty filter or a frozen coil causes the majority of them. Those are usually easy fixes. The trouble starts when the water just stays there. It can damage drywall, warp floors. Grow mold.
So if you find water today turn the AC off. Run through the basic checks. If it leaks again have someone take a look. A short visit now beats a repair later. If you are wondering what that visit might cost our post on AC repair cost in Los Angeles County has some typical numbers.
Is Your AC Leaking Water? Get Help Today
Still seeing water around your air conditioner? Don’t wait for it to damage your ceiling or floor. Call AOL Heating & Air at 818-705-0000. We will find the cause explain it in words and fix it the right way so the leak stays gone.
