This is why Split-Type air conditioner units begin leaking


When a split-type air conditoning unit begins leaking, 99% of the time it’s the result of a blocked drainage line. Besides the cooling function, an air conditioning system is also very effective at removing moisture from the air to provide a comfortable environment. The moisture collected must go somewhere, it does not simply disappear. As the HVAC system removes moisture from the air, it collects as condensation on the evaporator coil that then drips into the drain pan. The liquid then travels through the condensate drain pipe to connect with the main plumbing to be dispelled. The condensation created by the system can be filled with dust particles as well as bacteria, and this leads to a build up of algae in the drain pan as well as within the drainage line.

The most common air-conditioning systems utilized in residences are Split-Type air conditioners and Window-Type air conditioners (also referred to as Box Units). Both of these AC systems rely on gravity for dispelling of the condensate from the drain pan through the drainage line. The drainage line for Window-Type units tends to become blocked less frequently, as more often than not, the drainage line is connected vertically to the drain pan which results in the condensate flowing rapidly through the drainage line. Contrast this to Split-Type AC’s where the drainage line often travels a significant horizontal distance before it connects with the main plumbing – thus the condensate travels very slowly through the drainage line, and condensate pools within the drainage line when the air conditioner is not operating. This inevitably leads to a build up of algae over time, which ultimately results in the drainage line becoming blocked, and the air conditioner will begin to leak as the condensate can no longer be dispelled. AirCare Solutions personnel flush drainage lines with several litres of water under high pressure for each and every AC that we clean as a standard operating procedire in our deep cleaning service. 

In order to avoid clogged drainage lines, we recommend that air conditioner drainage lines are flushed twice per year – and at the very least, at the end of the summer season when your AC’s are no longer in use. It’s important to note that when algae is left within drainage lines over the cooler months when AC’s are not in use, that the algae will dry and harden and solidify. Over time, layer upon layer of solidified algae will constrict the drainage line and thus the consequence is more frequent occurences of blockage. Constricted drainage lines are akin to the arteries of a person with a diet high in cholesterol – eventually it’s going to present a serious problem! Once the drainage line has become severly constricted by several layers of solidified algae, simply flushing the drainage line with water under high pressure is not enough to remove all of the debris. At this point, the only effective method to clear the solidified algae is with a chemical flushing (a similar process to clearing blocked plumbing in a kitchen or bathroom sink).

How AC’s and their drainage lines are installed can have a significant impact on the frequency that the drainage lines become blocked. If you discover that one or more of your AC’s are frequently leaking as a result of blocked drainage, then this is typically the result of one or more installation issues;

(i) It is commonplace for Air Conditioning Systems to have been poorly installed which can lead to higher frequency of blocked drainage. For example, we often come across drainage lines that have a positive incline at some point along the drainage line (often immediately after the connection point to the drain pan). This leads to far more rapid development of algae within the drainage line, and often within the drain pan itself.

(ii) It is commonplace for Split-Type Air Conditioning Systems to have been poorly installed. Split-Type AC’s are supposed to be installed at a slight 1-degree to 2-degree negative incline towards the side of the AC where the drainage line has been attached to the drain pan. We often find that Split-Type AC’s have been installed completely level – this leads to pooling of water within the drain pan which in turns leads to more rapid development of algae both within the drain pan as well as within the drainage line.

(iii) It is commonplace for Air Conditioning Systems to have been poorly installed with multiple AC drainage lines converging into a single drainage line before exiting to the main plumbing of the building. These kinds of installations present a whole host of problematic issues that inevitably result in frequent drainage line blockages. The worst-case scenario is when the single drainage line, that multiple AC drainage lines have converged into, becomes blocked in which case multiple AC’s may begin leaking simultaneously. This type of installation can even result in one or more AC’s leaking when they aren’t even in operation. It is common to find these kinds of poor drainage line installations in various residential developments throughout Hong Kong. In apartment layouts where there are a number of bedrooms connected via a corridoor from the living/dining room, it is commonplace to find that there is a false ceiling running the full length of the corridoor, and all of the AC drainage lines will converge into a single drainage line hidden within that false ceiling area.

(iv) Regardless of how well an AC and its drainage line has been installed, owing to the very nature of the composition of condensate running through a drainage line, it is unavoidable that algae will develop over time within any given drainage line. Any algae that is left within a drainage line for long periods of time (for example during the cooler months when an AC is not being utilized) will harden and constrict the drainage line. The long-term result of inadequate maintenance of AC drainage lines is that drainage lines will eventually become so constricted (or entirely blocked) by hardened algae and/or other debris and the condensate is no longer able to drain freely.

Drainage line that has become almost entirely constricted by layer upon layer of solidified algae over time

Drainage lines that have become constricted by hardened algae over long periods of time may have appeared to have had no significant issues for several years – but once the drainage line reaches a similar condition to the above image, blockages will occur far more frequently. The above image is a perfect example of why it is so important to ensure that your AC’s and their drainage lines are cleaned and flushed twice per year, and most definitely at the end of the summer season.

Here’s a short clip of a dirty AC with a blocked drainage line:

If one or more of your AC’s are suffering from persistent dripping issues, then it would be wise to arrange for AirCare Solutions personnel to conduct an inspection of the problematic AC(s) to identify any installation issues of the AC and/or the drainage lines. After the inspection, our personnel can then advise cost-effective recommended solutions (there’s often more than one way to resolve installation issues) and provide you with a quotation for the recommend course of action.

For a significant proportion of cases of where drainage line blockages have been occuring more frequently than would be considered within a normal timeframe, it’s typically best to arrange for a chemical flushing of the drainage line to ensure that the problematic drainage line is entirely cleared of calcified algae and any other debris – and whilst our personnel are there, they can also conduct a thorough inspection of the drainage line installation to identify any defects and provide recommended solutions.

Bookings for chemical flushing are charged at $1,200 for one AC drainage line, and $400 for each additional AC drainage line. Should chemical flushing of a drainage line be required whilst our personnel are already attending to your AC’s for a standard deep cleaning booking, the fee is $400 per instance. Please note that for shared drainage line installations, all of the AC’s that share the single drainage line must be dismantled in order to ensure that the process is successful, as well as to ensure the protection of delicate electronic components.

If it’s a real emergency and you’re unable to get a booking with us within a day or two to resolve a blocked drainage line issue, then you may wish to try to resolve the issue yourself after watching the brief instructional video below. For the vast majority of Daikin ACs, it’s a relatively simple process just like the video – but it should be noted that with most other brands of AC, it’s typically more challenging….and with some brands of AC, just downright cumbersome! If you’re in doubt, it’s obviously best to wait a short while to have one of our professional HVAC technicians take care of it for you.

Depending upon which brand and which model of Split-Type Air Conditioning system you have, it can be a relatively simple process to unblock the drainage line – which is the most common cause of a split-type AC system to start dripping. Daikin ACs are particularly well designed, and the vast majority of their ACs have been engineered with ease of dismantling and ease of deep cleaning as priority features.

So if you’ve got a split-type AC that has a blocked drainage line and you’re handy with a screwdriver – you may want to try unblocking the drainage line for yourself if you’re struggling to get an emergency booking with a professional HVAC technician.

Please note: This is an impromptu video where we had invited the client to film the process after he had expressed an interest to learn how he could unblock a drainage line by himself. So it was filmed on the fly with no preparation, no script, and in a single shot with no other camera angles apart from a brief close-up of the algae that had caused the blockage. At a later date we will be preparing a more professional video with greater detail, better/closer camera angles for the various steps in the process, as well as demonstrating the process with a few other AC brands as well. Disclaimer: ACs are electrical devices, so be sure to isolate the power by turning the AC off at the Circuit Breaker in the Main Fuse Box of your home. Simply turning it off with the remote control does not completely isolate the power.

It should also be noted that AirCare Solutions personnel will utilize a pressure washer to flush drainage lines out – not simply the pressure from one’s lungs. This clip was prepared purely to demonstrate that it can be a relatively straightforward task to unblock a split-type AC condensate drainage line with just a screwdriver and a short length of standard garden hose. Lastly, it should be noted that drainage pans, condensate, and condensate pipes, can contain significant levels of bacteria – so one should take care not to ingest any condensate if using ones lungs to force air pressure through a drainage line.