5 Common Reasons For Your Aircon Leaking

Nobody wants to wake up at 3am to a drip-drip sound coming from their leaking aircon. If left unchecked, that drip could get worse, and soon you will discover puddles under your aircon every morning.

The water can seep into the walls or floor, or grow mold and harm our health.

Here are the main causes of air conditioner leaking:

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Reason 1: Overflowing drain pan

An aircon works by blowing normal temperature air over a set of cooling fins. As the normal air flows over the cold fins, the moisture is taken out of it, and it gets cooler.

But, that moisture has to go somewhere. So all aircons have a little tray at the bottom, called a drain pan, to collect the water. Then, the water will be channeled outside through a small drainage pipe.

But, if the water is not draining properly, it will fill up the drain pan and overflow, spilling out into your room.

What could cause the drain pan to overflow with water? It could be due to build of up slime or dust over time, making the drain pan shallower than usual. Getting your aircon cleaned regularly should take care of that.

aircon drain pan
The grey plastic tray under the cooling fins (known as the drain pan) collects condensation and flows the water to a drainage pipe that leads outside
Aircon trunking containing gas coolant pipe and water drainage pipe
This aircon’s drainage pipe is on the right side, so the drain pan must be tilted slightly towards the right to allow the condensation to flow away

 

Aircon compressors along shophouses
Walk along the back lane of any row of shophouses, look up and you’ll spot lots of these drainage pipes leading to the ground.

 

Reason 2: Tilted AC blower unit

For an AC blower unit (the indoor unit) to function properly, the unit must be tilted slightly toward the drainage pipe. This is to ensure any condensate water will flow towards the drainage pipe. If not, then the water will simply pool up on the opposite end and overflow.

What could cause the blower unit to tilt the wrong way? It could be caused by sagging. Over time, the bracket holding up the unit may shift or sag, or the unit was not put back properly after a previous servicing. This will cause the condensed moisture to be unable to flow away, and spill down the front of your unit and on to the floor.

Aircon leaking can damage parquet flooring
Aircon leaking can damage parquet flooring!

 

Reason 3: Dust buildup and mildew growth

This is the most common problem for most AC units that don’t have periodic scheduled maintenance.

Presence of dust and mildew will clog the air filter and drainage system if it is not cleaned properly. Clogging in this area will cause water from the condensed moisture to find other paths to flow, and eventually, the water ends up going down your walls.

“Dirty or blocked drain pipes are usually the main reason for AC leaks,” – The Dustbox

 

Aircon servicing malaysia

Reason 4: Dirty filters and coils

During cooling, warm air flows through an air filter and through a series of cooled coils to cool down.

However, dust buildup on the filters and cooling coils will slow down the air flow. As the buildup increases, ice can form around the filter or coils. When the unit is switched off, the ice will melt and cause water to drip from your indoor unit.

Dirty air con filter
Don’t let your aircon filters reach this state

 

Reason 5: Air leakage or poor sealing

It is important to make sure the pipe that carries the liquid refrigerant from the outside compressor to the inside coils is sealed and insulated properly. If those pipes are not properly sealed, or you have a refrigerant leak, then a lot of water condensation can form on the pipes or AC unit, which can drip down into your room.

As a result, you will see water droplets clinging onto the AC unit, and eventually, dripping on the floor. Service your aircon regularly to make sure everything is properly sealed and closed.

 

How to Prevent Further Aircon Leaking?

Air-conditioning units have become almost essential, so having a leaking AC can be incredibly disruptive.

However, they are also relatively easy to fix, as long as you hire a specialist who can figure out the problem, and do the necessary repairs.

Regular servicing is important to keep your aircon unit in good working condition, so you should not put it off for months (or years!).

 

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This article was first published in 2 March 2016, and updated on 5 Oct 2024

14 thoughts on “5 Common Reasons For Your Aircon Leaking”

  1. One point I really don’t understand. It says it is important warm air doesn’t get into the aircon unit. I thought the whole point is that the warm air in the room gets drawn into the unit to be cooled and blown out again. If the air being drawn in is not warmer than the air going out it is not an air conditioner. It is a fan.

    1. Hi Tim, actually I was referring to the pipe that carries the liquid refrigerant from the outside compressor to the inside coils. If those pipes are not properly sealed, then a lot of water condensation can form on it, which can drip down into your room. I have edited the article. Sorry it wasn’t clear!

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  3. I am not a AC service pro but I have struggled with different service contractors over the years. Here are some of my take-aways:

    1. Don’t allow your AC compressor (the part that sits outdoor) to be cleaned using chemical wash. Unless the coils are caked with dirt over many years.. avoid this – the chemical used are strong acids which thin the coils with repeated cleans (eventually resulting in the coils breaking and a new unit will have to be bought). These coils can be cleaned by using a water spray or hose pipe (taking care not to wet any electrical points) while having the unit running or I am told, run the unit while its raining for about 30 mins. The outside unit is designed to be resilient moisture damage. The cost of chemical clean is just another way the AC contractor adds to your service charges.

    2. The interior unit needs to be cleaned regularly – really depends on the use of the AC unit. I get mine done every 3 months which prevents and mold and mildew build-up which may cause water outflow blockages.

    3. Every 12-15 months, you should get your AC contractor to do a full-strip down of the unit from the wall and take it apart to have it cleaned and washed thoroughly. This is different from the regular 3 month service. My AC contractor calls this a MAGIC clean.

    4. Do not be conned by your AC contractor when he tells you he need to top-up your gas coolant.. especially if you notice its done fairly often. The coolant in your AC is now just like the one in your fridge.. its does not need toping up unless there is a leak in the system. It’s a fully self contained system. A top-up may only be required once every 5 years or so.

    This is my position, over the last 10 years of dealing with different levels of professionalism within the AC service industry.

    1. OMG Thank you thank you thank you. What worried me as much as a conman as my technician, is also to know whether he is incompetent. Since I am not an expert in aircond world, I usually would just agree on whatever he says during installation or repair. Some technicians would also be unhappy if I “instruct” them to do the thorough job (for example every steps mentioned in this article). Would you give us more insight on this issue too? Thanks a bunch!

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  6. Hi, my unit in my room (used daily) keeps leaking water once every few months. My service guy says the leak occurs because of blocked drainage and that the AC needs to be serviced once every few months. but i had no water leakage problem for the previiis units for years (without regular servicing). Is this normal and right? It’s getting really frustrating. Every time they come due to a water leakage they just ‘blow’ the pipe to force everything out and then it lasts for a few more months before there’s another water leak again.

    1. Hi Shiyang,

      I am sorry to hear about the repeated leakage problem that you are facing. I totally understand the situation that you are going through, having paid the professional fees and yet the problem keep coming back leaving you alone to face the problem and continue paying unnecessarily.

      First of all, as i have not seen the actual air con unit whatever i am saying has to be taken with a pinch of salt.

      The most common reason for leakage is indeed a blockage in the piping resulting a reverse flow of water dripping into your indoor area.

      It is a common practice to do the blowing, however there are different severity when it comes to this leakage.

      Your issue could be a hardening of gel form dust instead of the primary stage of blocking. When the technician came to do the blowing it only clears off partial of the blockage resulting to a returning problem.

      We understand the problems that customers is facing therefore we provide a 6 month warranty on all our job completed so that our customer can have a truly ultimate peace of mind when they engaged us.

      We would love to take up your case and solve your problem once and for all.

      Hotline: 014 6300 060

      Sorry that our website is currently down as we are in the process of revamping our online presence.

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  9. Absolutely! If you find an air conditioning leak, address the issue immediately before you have a real problem on your hand. Leaking air conditioners can destroy ceilings, walls, and anything else around it.

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