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What You Should Know About Leaking AC Units

Leaking AC UnitsAir conditioning is found in most homes and apartments, and anyone with an AC unit can have trouble imagining life without the perks of temperature control. While useful for fighting back against the summer heat, AC units can also be the source of headaches if they begin to leak. If there is an AC unit dripping water inside, structural problems can result as water infiltrates your walls and floors. A window AC unit leaking water can cause problems inside or outside the home. Although an AC unit leaking water on floors, walls, etc. isn’t as troublesome as, say, a flooding dishwasher or overflowing toilet, it is still a problem that needs to be addressed.

Causes of Air Conditioning Leaks

Clogged Drain Lines

Air conditioning units produce a fair amount of condensation, which is normally collected in a drain pan and siphoned away by a drain pipe. One of the most common causes of an AC unit leaking water is that there is a clog somewhere in the drain line—usually caused by dirt or rust, but algae has been known to grow in the pipes as well. These clogs cause water to back up and eventually make the drain pan overflow and spill into the surrounding walls and floors.

Loose Drain Line

If improperly installed, the drain pipe may not be sufficiently secured. Over time, it can loosen and disconnect from the main unit entirely. This results in an AC unit leaking water either outside or inside directly onto the ceiling or floor, depending on where it is located.

Cracked Drain Pan

If the drain pan is faulty or damaged, it can develop cracks that allow condensation to seep out into the surrounding structure. This, like other forms of AC leakage, creates damp patches and builds up water damage over time.

Installation Error

AC units take advantage of gravity to direct condensation towards the drain pan. If a unit is angled the wrong way while being installed, some of this water may flow away from the pan and drip into the home.


There are coils within the AC unit that are susceptible to ice buildup. This usually happens if the unit is being run constantly (like in the summer) or is operating when the temperature is below 60°F (like the in winter). The ice creates obstacles that redirect water away from the normal drainage paths and can cause leaks. Alternatively, the ice can damage the structure of the unit if it builds up to a significant degree.

Poor Duct Insulation

Condensation can build up around your air ducts if they are not properly insulated. The reason this happens is fairly simple: as cool air passes through the ducts, it can chill them to the point where, combined with the ambient temperature, they act like a cold glass on a hot day. This leads to condensation building up around the ducts and vents, and it can spread from there through the ceiling or floor. Properly insulating the ducts is often the key to preventing this scenario.

Lack of Maintenance

One of the most common causes of air conditioners leaking water is a lack of maintenance. Since it is typically located in the basement and other hidden areas of the home, it may take days for you to notice any leaks. Unfortunately, if your gravity drain line carries condensation into a drain pan, which is pumped out by a condensate pump, you may have an issue. These setups can lead your air conditioner to leak water inside of your house. This can happen if the older drain pan is rusted, developing holes and cracks, or if the condensate pump breaks down, causing the pain to overflow.

Frozen Coils

Central air conditioners may be designed to work extra hard in very high temperatures. It is normal for ice to form in the evaporator coil. When the ice melts, the water leaks out. If the coil has been frozen it can cause problems with your air conditioning system. For example, you can end up with a fried compressor, which is extremely expensive to fix. In the worst-case, you may need to replace the entire unit. If you are not using your air conditioner, you should turn off the system. If the coil freezes, turn your AC off for a few hours to let the ice melt and make sure to soak up any leaking water immediately. If this continuously happens you should call the professionals to assess the problem and find a resolution for you soon.

Change Air Filters

Clogged air filters can also pose problems. If your air filter has been clogged it restricts the amount of air that your AC can pull into your home, leading to future problems. Changing your filters is a good way to keep them running in good condition and prevent water damage due to air conditioners.

Air Conditioner Water Damage Cleanup Tips

Inspect It Regularly

Regular inspections of your AC system will go a long way to keeping your property protected and your appliances working well. When it is running, check the condensation line opening to make sure that you see water flowing into the drain. You can find out how much humidity is in your house based on the amount of water you see.

Monitor Clogged Drain Pipe

You should also be cleaning your drainpipe regularly. You can do this quite simply by using a nylon string and a small piece of cotton rag. Using a shop vacuum, you can suck out the nylon string on the next side and then tie a small piece of cotton rag to the other end and pull through. This will bring all of the debris inside the line out of the exit side. Of course, do not make the rag piece too large as it will get stuck. You can also use a condensation pump to help move the water out, but you should consult with the professionals before you try this method.

Assess the Air Filter

Assess your filter to find out if it is dirty or full. If it is either of those, ice can form on your unit evaporator coils and melt water from the unit. Filters generally last for a month or two, but if you use your system a lot in the summer you should replace it every 30 days to prevent problems. If it looks dirty, swap it for a new one.

Contact Flood Services Canada for Professional AC Leak Cleanup and Restoration

Should you end up facing water damage from a dripping or leaking AC unit, professional remediation can be used to fix the problem and thoroughly inspect your property for damp patches and water damage. When facing water damage, Flood Services Canada’s quick-response teams of professional remediators will drain, dry, and save your property.

Contact us at (416) 302-2107 for more information about air conditioning leaks, or use our emergency hotline at (416)-999-3930 to get our rapid-response teams deployed to your location.

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Chad Vanvari

Chad Vanvari has over 20 years of experience as a cleaning & restoration professional. He started out in Montreal, establishing a commercial carpet cleaning company in the early 1990’s. By 2001, Chad had relocated to Toronto and now had extensive knowledge and experience in responding to fire/water related emergencies. He has been instrumental in the cleanup of several catastrophic floods. Currently, Chad is the president and owner of Flood Services Canada, a 24/7 emergency service restoration company.