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We've Sprung a Leak: 4 Reasons Your AC Is Leaking

cartoon home flooding

On a long hot Texas day, we’re always thinking about water: swimming holes, icy cold drinks, even those rare summer rainstorms. One place we’re not crazy about finding water? Pooling around our air conditioning unit. If your AC is leaking, turn it off immediately. Then, read on to uncover possible causes and solutions

Water, Water Everywhere

First things first: why is there water in your AC unit anyway? Air conditioning works by using an evaporator coil to cool air. As the air cools, condensation forms. (Take a nice cold glass of your favorite beverage outside on a hot day to watch condensation in action.) The condensation runs down the coil, into a drain pan, and out through a condensate drain line. Usually, a leak means that one of these components isn’t working as it should.

A Flash in the Pan

Possibility #1: a cracked drain pan. If your drain pan has cracked or rusted through, it’s not able to hold the condensed water, which will then leak out. This is especially common in older units. Replacing the drain pan should easily fix the problem. If your unit is brand new, it’s also possible that it wasn’t installed correctly. If the pan or the unit isn’t level, water might be overflowing on one side.


Possibility #2: a dirty air filter. If your air filter is clogged, it blocks the flow of warm air over the evaporator coil, causing the coil to literally freeze. When the ice on the coil melts, it may overflow the drain pan, causing the leak. We recommend changing your air filters every three months (more often if you have pets). If remembering to change your filters is a hassle, consider signing up for a filter delivery service.

On Down the Line

Possibility #3: a clogged condensate line. The condensate line can easily become backed up with dirt, sludge, or mold. When that happens, the water has nowhere to go, so it ends up overflowing the drain pan. You can try unclogging it on your own using a wet/dry vac, but you’ll probably want to call for professional help. Your HVAC specialist can clear the blockage and check for any damage it might have caused to the pipe. A clogged line is the most common cause of AC leaks, but it is preventable — pour some chlorine bleach down the line every six months to prevent buildup.

Is Your Refrigerant Running (Out)?

Possibility #4: low refrigerant levels. Much like a dirty air filter, low refrigerant levels will cause the evaporator coil to freeze over, leading to an overflowing drain pan when it melts. When refrigerant is low, you’ll also notice that the unit isn’t cooling, and you might hear a hissing or bubbling noise if the low level is due to a leak. Definitely call in the pros for this one. If there is a leak, you might need to replace your entire unit.

Most AC leaks aren’t a big deal and can be repaired easily. The key is catching them before they get out of hand. Check your AC unit regularly for leaks or other indications that something isn’t working quite right. If you suspect an issue, give your HVAC specialist a call.

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