Why Is My AC Leaking Water? 5 Common Causes and How to Fix It
Cold air should be the only thing coming from your AC this summer
Highlights
A clogged drain line, dirty air filter, broken pump, and more can cause your AC to leak.
You’re better off leaving some fixes, like a broken pump, to an HVAC pro.
Regular AC maintenance costs between $75 and $200.
When you notice your AC leaking water, it’s all too easy to shrug it off as some harmless condensation. But any time you have water leaking in your home, it’s time to take a closer look. Diagnosing and solving the problem swiftly can be the difference between an easily fixable leak and needing to replace the AC system and repair your water-damaged drywall. Here are five common causes for an AC unit that’s leaking water.
1. Clogged Drain Line
The line that carries the condensed AC water from inside your residence to the sewer drain can become plugged with sludge or debris over long periods of time. Dust, dirt, mold, and deposits from the water get left behind and dry, building up layers that eventually clog the drain line.
How to Fix
You can uncap the end of the drain line and use a wet/dry vacuum to suck out any solid debris. Or, you can rinse the line with vinegar to clear out algae or other damp debris buildup stuck in the line.
However, it’s best to leave unclogging an AC drain line to an HVAC repair pro. You could cause further damage to the drain line or other parts of the air conditioner if you make a mistake. An AC repair specialist may use nitrogen or a snake to quickly remove clogs deep in the line without damaging the AC unit.
2. Dirty Air Filter
As with most systems using an air filter, the intake air gets pulled through the filter, which catches dust and debris to keep it from causing problems inside the rest of the system. Because condensation and evaporation are such essential parts of the air conditioning process, the AC can’t run as efficiently when the air filter is dirty and restricts airflow needed for evaporation. This leads to the evaporator coil getting very cold and developing ice that builds up, eventually melts, overwhelms the drain pan, and leaks inside your home.
How to Fix
Thankfully, it’s easy to replace your air filter to prevent this from happening. You’ll need to note the type and size of filter you need, which you should be able to determine with your user manual or on the side of the old filter. Buy the right filter replacement at your local hardware store or online. AC filters work best if you change them out at least every 90 days.
3. Refrigerant Is Low
Low refrigerant is another possible cause of water leaking from your AC; low refrigerant can also lead to freezing evaporator coils and the melting that follows. Most often, slow refrigerant leaks in the valves or fittings of the air conditioning system itself cause low refrigerant in your AC.
Some signs that your refrigerant could be low include:
Your AC doesn’t cool your home like it used to or like it should
Noises like bubbling or hissing coming from the AC unit
Freezing lines
Water leaking from your AC, of course
How to Fix
If you notice your AC leaking water and have ruled out other issues, like a dirty air filter or clogged line, have an HVAC expert come check the refrigerant, which could be low or even leaking.
Checking and refilling the refrigerant in your AC should be left to an HVAC professional because, according to the U.S. Environmental Protection Agency (EPA), air conditioning refrigerants can be toxic and flammable.
4. Damaged Drain Pan
If you don’t see any frozen lines or the drain pan full of water, the drain pan itself could be leaking.
The drain pan is what collects water from condensation dripping off the evaporator coil and directs that water to the drain line. Drain pans that are made from metal, like galvanized steel or stainless steel, can corrode over time. This corrosion can damage the metal, leading to leaks. Although polymer drain pans are resistant to rust, they can still crack.
Your drain pan can also leak if someone installed it improperly. If the drain pan doesn’t sit just right, it won’t drain the water away. Instead, it will fill up with water and eventually overflow.
How to Fix
Check for rust, cracks, or other damage to the pan. You can repair cracks with caulk or another silicone sealant. You need to replace a pan that’s rusted through. Just make sure it’s the right fit for your unit. If the drain pan is leaking because of improper installation, it’s time to call in the pros to fix the placement of the pan.
5. Broken Condensate Pump
This pump is located beside or directly on your furnace and pumps condensate water out of your home. When it stops working, the water stops moving, and leaks can start.
Condensate lines can also become clogged, preventing the water from flowing outside of the home. Instead, water will flow back to the drain pan and begin leaking.
How to Fix
A broken pump warrants a call to your local HVAC pro, as they’ll need to install a new one, which involves working with electrical. Don’t try DIY repairs here because it’s dangerous and could void your warranty.
Tips to Maintain Your AC Unit and Avoid Leaks
Doing some relatively easy routine maintenance can go a long way in preventing breakdowns and other issues like water leaking from your AC. This can also help keep your AC running more efficiently. Most of the following list is quick and easy for you to do on your own, but be sure to have a local air conditioning pro check the technical stuff every year.
Keep the AC unit outside clear of any leaves or other debris that may block or restrict airflow.
Check your drain line for blockages or buildup, and clean it out with a shop vac or compressed air.
Change the air filter every month during the summer months.
As the weather warms up, have a pro inspect your AC to catch any issues before they become more costly and leave you without cool air when you need it most. The average cost of an annual AC tune-up is $150.
Is It Time to Contact a Pro?
A leaky AC isn't an immediate cause for professional help. Once you find a leak and identify the cause, you can determine whether it’s a job suited for your experience. Even beginner homeowners can handle unclogging a drain line or replacing an air filter. More advanced issues, especially those that require fixing refrigerant leaks need an HVAC professional with average HVAC repairs costing around $350.
Jouviane Alexandre contributed to this piece.
Frequently Asked Questions
Yes, you can run your AC if it’s leaking water. Water is a natural by-product of air conditioning units, and even if it’s leaking water, your AC will continue to work. Unlike refrigerant, leaking water doesn’t pose any health risk; however, just because you can run your AC doesn’t mean you should. Leaking water can cause damage to your home, especially if the leak is indoors. The cost to repair water damage ranges between $3.75 and $7 per square foot but ultimately depends on the extent of the damage. If you notice a leak, it should be repaired ASAP.
No, your AC will not stop leaking by itself. A leaking AC is caused by issues like clogged drain lines, dirty air filters, low refrigerant, or a broken pump. All of these issues require troubleshooting and need to be fixed by you or — in the case of working with refrigerant or a broken pump — an HVAC professional.