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Aircon Unit Flushing: Is It Important?

What is an aircon system flushing?

An aircon flush is a service or preventative maintenance that can be performed on cooling systems to clean sludge and sediment from the hoses and drains and all parts of the aircon unit while checking for leaks. Cleaning the aircon unit helps prevent damage to the compressor and other parts of the aircon unit like the condenser.

An aircon system flush involves running a liquid solvent through, with vacuum pressure to clean the inside components of your aircon unit. A clean, flushed system lasts longer so preventative or planned maintenance checklists should include this scheduled aircon maintenance. A professional aircon servicing company is responsible for the disposal of any evacuated coolant in an approved manner when completing an aircon system flush.

Why is an aircon system flushing important?

An aircon system flush is a necessary procedure to ensure the entire aircon unit is clean and free from any contaminants. Any foreign objects in the aircon unit can cause blockages and prevent the compressor from operating efficiently. It is ideal when replacing a compressor to replace a thermostat expansion valve and we should be reminded that this should be done every time that a compressor is replaced.

Evaporator coils are also critical to be flushed. Imagine a compressor failure and it pumps filings through the system and blocks the valve. As the compressor is failing any filings build up in the filter drier the compressor pumps until the aircon unit is cut off. The vacuum that is pulled in the suction side of the aircon unit means that all filings and oil in the compressor are sucked straight into the evaporator coil, and as a result, the evaporator coil will be full of filings.

When should an aircon system be flushed?

It is recommended for an aircon unit to be flushed when you have the following reasons:

1) If the aircon unit is contaminated as a result of any component failure, then the whole aircon unit should be flushed properly and purged.

2) If the aircon unit has a dryer for the refrigerant, then it is highly possible to get corroded and get rusty due to the moisture content of the refrigerant.

3) It is also advisable to flush one component at a time. Flushing should also be done in the different or opposite direction of the refrigerant.

How to perform an aircon system flushing?

Step 1:

Before starting work at the aircon unit, check the flow direction. Principally it should be in the following order: compressor, condenser, drier, expansion valve, evaporator – for an aircon unit with expansion valve or compressor, condenser, orifice tube, evaporator, accumulator – for an aircon unit with an orifice tube.

Step 2:

Recover the refrigerant from the aircon unit and remove the compressor and drier for an aircon unit without an expansion valve and also remove the orifice tube.

Step 3:

Prepare the aircon unit flushing supply set V99-18-0067 by installing a valve, hose, and flush gun on the can. Inject the flushing agent with the pressure in the can. Flush against the flow direction.

Step 4:

Follow the flush with compressed nitrogen or pressurized air (at 8 bar/120 PSI max.) to increase mass flow for maximum cleaning to finally exit the system with the dirt.

Step 5:

Repeat the procedure for the next part of the line. The amount of flush needed to adequately clean and flush will vary due to the length of the line to flush. An approximate value would be 50% of the can for the condenser side and 50% of the can for the evaporator side. Exact instructions are listed in the product manual.

Step 6:

It is recommended to install an in-line filter to avoid problems with residues that are left in the system as a hazard. Pull a vacuum after assembly to remove any residual solvent. The line set is clean and ready for service.


It’s always a good time to talk about the common issues that aircon units have. This way, you’ll be able to spot if there are problems with your unit or not and prepare for its replacement accordingly. If you require our aircon servicing services, Whatsapp us at +65 9222 4141 for a fast and transparent quote.

338 Aircon Servicing Singapore provides an extensive range of Aircon Services including Aircon Servicing, Aircon Repairs, Aircon Installation of the best aircon brands, Chemical Overhaul, Gas Top-up, Aircon Leaking Water, and Aircon Not Cold Fix, and more. We have a team of professional technicians who are equipped with vast knowledge and experience in the Aircon industry.

We have over 15 years of experience in dealing with aircon works and have completed thousands of aircon works for both residential (Landed, Condo, and HDB) and commercial. We are a highly recommended Aircon Company in Singapore, with many delighted customers and reviews over the years on Google and Facebook.

WhatsApp us at +65 9222 4141 for a transparent quotation and honest pricing for all your aircon needs or Call us at +65 9222 4141. We offer a fast and efficient service to serve any of your aircon needs!


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