Updated On

May 27, 2024

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    The most common reason AC units stop draining water is due to a clogged condensate drain line. When this happens, water backs up and overflows from the drain pan — this can cause serious water damage, mold growth, and other expensive problems in your home.

    In this guide, I’ll explain the main reasons why your AC may not be draining water and what you can do to fix the problem before it leads to costly repairs. I’ll also share some tips on how to prevent clogs in your condensate line to keep your air conditioner running smoothly and prevent water damage.

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    When Does Your Air Conditioner Drain Water? 

    Water does not always drain from your air conditioner. There are times when your AC may drain more water than others. The factors that affect condensation include: 

    • Outdoor air temperature
    • Indoor air temperature
    • Air conditioner condition
    • Air filter maintenance

    However, air conditioners pull air through the air handler, where the evaporator coil cools it. During the cooling process, condensation forms as the system cools the air and removes moisture from it. 

    The condensation collects in a drip pan connected to the condensate drain line. Usually, the water drains outside your home. 

    When the drain pipe gets clogged, water collects in the A/C condensate pan. During the colder months this could lead to you fixing a frozen AC drain line. If you do not clear the blockage, the drip pan could overflow, causing significant water damage, mold, and mildew.

    What Should You Do When Your HVAC Is Not Draining?

    Anytime you suspect that your AC is not draining correctly, you must take action immediately. So, here are a few steps you can take to prevent any damage to your property. 

    Turn Your Air Conditioner Off

    Anytime you perform maintenance on your HVAC system, you need to turn it off. There are moving parts that can hurt you, or you can damage if you attempt to work on the AC when it is on. 

    Check The Drain Pan

    Under the evaporator, you will find your AC drip pan. First, you should check for standing water. If you do find water, the line is clogged. 

    When the drain pan is empty, but water is not draining, it could mean that the condensate drain pipe has come undone. 

    Clean Up Water

    If your air conditioner drip pan has already overflowed, you will need to dry the water as soon as possible. If possible, use a wet/dry vacuum to remove standing water and anything in the drain pan. 

    If water leaked into your insulation or caused mildew or sheetrock damage, it is best to call a professional company because mold and mildew can harm your health, and the longer you leave it, the worse it will get.

    Clear The Drain Pipe

    After you protect your home from water damage, you need to clean out the condensate line. Luckily, the process is relatively straightforward. 

    1. Make sure the drain pipe is connected to the condensate pan. 
    2. Locate the drain pipe outside your home, and place a bucket under it.
    3. Use a wire brush to remove any slime or debris at the end of the line.
    4. Next, locate the condensate drip pan access point. 
    5. Pour a mixture of one cup of bleach and a gallon of water into the drain pipe and allow it to sit for 30 minutes. 
    6. Check the bucket to see if the A/C condensate drain line is properly draining. 
    7. After the clogged drain clears, you should be able to pour water into the pipe, and it should immediately flow out. 

    If your air conditioner unit is still not draining correctly, you should contact an HVAC repair contractor.

    For more information on how to clear a clogged drain pipe, check out this video:

    Is There Anything You Can Do To Prevent A Condensate Drain Line Clog?

    Proper maintenance is the best way to prevent most air conditioner malfunctions. However, it is normal for drain pipes to clog from time to time as sediment, limescale, dust, and debris fall into the drip pan. 

    As the water moves through the pipe, the buildup can get stuck, causing the water not to drain. Resulting water damage can happen quickly and cost thousands to repair. 

    While you can’t prevent clogs completely, changing your filters regularly, maintaining your air conditioning unit semi-annually, and cleaning your condensate pipe and plan periodically makes a big difference. 

    During your routine maintenance appointment, the contractor will check the thermostat, refrigerant levels, check all PVC pipes to ensure proper connections, and perform any necessary maintenance.

    At the very least, having your system maintained by a licensed HVAC technician will help your system run more efficiently and reduce the amount of water your unit produces. It also gives the air conditioning service the ability to diagnose any minor unseen repairs, including clogged drains, before they become worse. 

    Could Your HVAC Not Draining Water Be A Sign Of Something More Serious?

    If your air conditioner is not draining, the most pressing concern for homeowners is that the drip pan will overflow, causing water damage. However, if your system is not producing the same amount of condensation that it usually does, that might be a sign that there is a bigger problem.

    The longer your air conditioner stays on before reaching the desired indoor air temperature, the more condensation the unit will produce. Some homeowners think their condensate drain has a clog, but after a repair technician visits their home, they learn the air conditioner is running inefficiently.

    If you have water leaking from your ceiling or suspect that something is causing your system to freeze or produce too much condensation, it is a good idea to contact an air conditioning service company

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    Final Advice When Your Air Conditioner Is Not Draining Water

    A/C unit problems are stressful. As a homeowner, you are responsible for paying for all necessary home repairs. A clogged AC drain line is never fun – but if you act fast, you can prevent devastating water damage and costly repairs down the line.

    In my experience, you can fix most drain issues with simple DIY methods like flushing the drain pipe with a cleaning solution or clearing the blockage with a wire brush. However, if your AC still isn’t draining after attempting these fixes, it’s best to call in a professional HVAC technician to diagnose and resolve the problem.

    Routine maintenance is key to preventing drain line issues and keeping your air conditioner in top shape. Have your system inspected and serviced by an HVAC professional at least once a year, and don’t forget to clean your drain line regularly.

    Frequently Asked Questions

    How do I know if my AC drain line is clogged?

    Signs of a clogged AC drain include water leaking around the indoor unit, a full drip pan, musty odors, and the AC shutting off unexpectedly. Check the drain line and pan for standing water to confirm a clog.

    How often should an AC drain line be cleaned?

    I recommend flushing your AC condensate line with bleach or vinegar at least once a year, at the start of cooling season. This prevent clogs and keeps your system draining properly.

    Can I pour vinegar down my AC drain?

    Yes, a 1:1 mixture of white vinegar and water can help loosen and flush out debris in a clogged AC drain. Pour it down the drain line and let it sit for 30 minutes before rinsing with plain water.

    Article Update Log
    Reviewed for accuracy, cost data, industry best practices, and expert advice by Jonathon Jachura.
    Editorial Contributors
    avatar for Alexis Bennett

    Alexis Bennett


    Alexis is a freelance writer with nearly a decade of experience covering the home services industry. She’s built considerable expertise in roofing, plumbing, and HVAC, as well as general construction and real estate matters. In her free time, Alexis enjoys coaching women’s golf. She lives in the Triad area of North Carolina.

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    photo of Jonathon Jachura

    Jonathon Jachura


    Jonathon Jachura is a two-time homeowner with hands-on experience with HVAC, gutters, plumbing, lawn care, pest control, and other aspects of owning a home. He is passionate about home maintenance and finding the best services. His main goal is to educate others with crisp, concise descriptions that any homeowner can use. Jon uses his strong technical background to create engaging, easy-to-read, and informative guides. He does most of his home and lawn projects himself but hires professional companies for the “big things.” He knows what goes into finding the best service providers and contractors. Jon studied mechanical engineering at Purdue University in Indiana and worked in the HVAC industry for 12 years. Between his various home improvement projects, he enjoys the outdoors, a good cup of coffee, and spending time with his family.

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