An unfortunate but common problem that many people have to deal with, is having their air conditioning unit leak water inside their home.

There could be multiple causes for this problem, and we will run through the most common ones.

But first, turn your AC’s thermostat to “off” to prevent further damage to your home.

Why does water form in my air conditioner?

Your AC’s inside unit contains an evaporator coil that cools the warm air blown over it. This causes moisture to form on the coil, much like how water droplets form on a cold glass of water on a hot day.

The condensation on the coil drips into a drain pan and down a condensate drain line (a white PVC pipe) that leads out your home.

So, let’s look further at a few things that could be causing that water to leak.

1. A clogged condensate drain line

This is the most common reason for water leaking into your home.

If the condensate drain line gets clogged with dust, dirt, sludge or mold, the water backs up. If your line is clogged, you’ll need to unclog it. There are different ways of doing this, and an easy method is using a wet/dry vac.

If you call in a professional air conditioner repair company, they’ll use a special vacuum to suck out the blockage material; you might as well try it yourself.

2. A rusty or damaged drain pan

If your air conditioner is more than 15 years old, it’s getting up there. Have a look at the drain pan. Is it rusted and allowing water to seep through holes? Maybe the pan is just plain damaged. In both of these cases, you’ll need to replace it.

3. Broken condensate pump

If you have an AC that is installed in the basement, you also have a condensate pump which pumps that water outside. However, if it breaks and isn’t working, the water is going to stay inside your home rather than being pumped outside. In that case, you will need to repair or replace the pump.

4. Dirty air filter

For warm air to flow over the evaporator coil and get cooled, it needs a clean air filter. If your air filter is dirty, the airflow is blocked, and the evaporator coil gets too cold and freezes over. When it melts, it drips an excess amount of water that may cause your pan to overflow.

Depending on the season, you should be changing your air filter every 1-3 months.

5. Low refrigerant

Another factor, which could cause your evaporator coil to freeze over, is that your refrigerant is low. Low refrigerant will lower pressure in your system. Your evaporator coil will freeze over, it will melt, and your drain pan will overflow.

There are a couple of signs to watch out for that’ll tell you you’re low on refrigerant:

  • The air conditioner isn’t cooling well
  • You hear a hissing or bubbling noise. This indicates a refrigerant leak.

If the leak is minor, you will be able to repair it. But in more severe cases, you’ll need to replace the whole AC unit.

Hopefully, you have managed to trouble shoot and repair your AC unit, and it has stopped leaking water. To safeguard against future leaks, it is a good idea to install a float switch on the unit if doesn’t have one already. This switch will shut down the air conditioner in case it overflows with water again. If you have run through the possibilities mentioned here, and your problem persists, call in a professional to find the solution.