Your aircon smells musty, drips water, or blows air that’s barely cool. You’ve Googled it, and now two terms keep coming up: chemical wash and chemical overhaul. They sound almost identical, some companies use them interchangeably (on purpose), and the price difference is real – $80 versus up to $150 per unit.
This guide isn’t about what each service is – we’ve covered that on our chemical wash and chemical overhaul pages. This is about the question those pages can’t answer for you: which one does your aircon actually need?
We do thousands of these jobs a year across Singapore, and the honest answer is: most people who think they need an overhaul don’t – and a smaller group keeps paying for washes when only an overhaul will fix the problem. Here’s how to tell which group you’re in.
The 30-second answer
Choose a chemical wash ($80/unit) if this is the first time you’re treating the symptom – a musty smell, mild dripping, weak cooling, or visible mould – and the unit has otherwise been serviced semi-regularly.
Choose a chemical overhaul ($100–$150/unit) if you’ve already done a chemical wash and the problem came back, the unit is 5+ years old and has never been deep-cleaned, or the leak/smell is severe and persistent.
The single most reliable rule we can give you: a returning problem is an overhaul problem. If a chemical wash fixed your smell or leak for only a few weeks, doing another wash is throwing money at the wrong service. The grime causing it sits in places that can only be reached by taking the fan coil off the wall.
Why the confusion exists (and how some companies exploit it)
Both services use chemicals on the fan coil. The difference is mechanical, not chemical: a wash treats the coil while the unit stays mounted on your wall; an overhaul removes the entire fan coil from the wall, dismantles every component – coil, blower wheel, water tray, casing – and washes each one individually.
That difference matters because some grime physically cannot be reached in-place: the rear face of the heat exchanger, the inside of casing seams, and hardened “bio-jelly” deep in the drain pan. No chemical poured from the front dissolves what it never touches.
Here’s the part worth knowing: some companies in Singapore sell an “overhaul” that never takes the unit off the wall. They do a chemical wash, charge overhaul prices, and the customer can’t tell the difference – until the problem comes back. If you’re paying for an overhaul, the fan coil should physically leave your wall. If it doesn’t, you bought a wash.
Decide by symptom
Musty or sour smell, first time. Chemical wash. Mould and bacteria on the coil and blower are the usual cause, and an in-place chemical treatment reaches them fine. If the smell returns within a few weeks, the colony is behind the coil or inside the casing – overhaul.
Water dripping, mild and recent. Chemical wash. The drainage flush included in a wash clears most early-stage clogs. Worth noting: if the actual cause turns out to be a poorly-gradient drain pipe or trunking issue, neither service fixes that – that’s a repair job, and we’ll tell you before doing anything.
Water dripping that came back after a wash. Overhaul. The drain pan has hardened sludge bonded to it. Once it reaches that state, it needs to come out and be washed as a separate part.
Weak cooling with normal gas levels. Depends on severity. If airflow feels weak and the coil looks dirty: wash first. If the gas has been checked, the filters are clean, a wash has been done, and the room still won’t cool – the coil is clogged from the inside. Overhaul. (If gas is low, that’s a different problem entirely – see our gas top-up page. No amount of cleaning fixes a refrigerant leak.)
Black mould visible on the vents or flap. Chemical wash, usually. Visible mould is front-of-unit mould, and a wash removes it. The exception is when it regrows quickly – fast regrowth means the source is deeper than the wash can reach.
Unit 5+ years old, never deep-cleaned, smells AND drips. Skip the wash, go straight to overhaul. We see this constantly with resale flats and rental units: years of compacted buildup that a wash will only partially dissolve. You’d pay $80 to discover what we could have told you upfront, then pay for the overhaul anyway.
Aircon over 8–10 years old and you’re deciding between overhaul and replacement. This deserves an honest inspection rather than a rule. An overhaul on an old-but-mechanically-sound unit can restore near-new performance for a tenth of an installation’s cost. But if the compressor is on its way out, the overhaul money is better put toward a new installation. We’ll tell you which it is – even when the answer earns us less.
The money logic, done honestly
Here’s the math worth doing before you decide.
A chemical wash is $80. An overhaul is $150 for one unit (cheaper per unit for multiple – $280 for 2, $390 for 3, $480 for 4, $100/unit for 5+), and includes a gas top-up if needed, which is itself worth around $80.
If your problem is a first-time symptom, the wash is the right spend – it fixes the majority of smell and drip cases, and paying double “just to be safe” is exactly the upselling we built this company to avoid.
But if you’re on your second wash for the same symptom, look at the running total: $80 + $80 = $160, and the problem is still there. The overhaul would have been $150, solved it once, and included the gas check. The most expensive option is usually the wrong service done twice.
One more honest note: a chemical overhaul is not an annual subscription, despite what some service packages imply. Done properly, most units need one every 3–5 years at most – and a unit on regular quarterly servicing may never need one at all. Anyone recommending yearly overhauls on a well-maintained unit is selling you labour you don’t need.
What we’ll actually do when you call
When you WhatsApp us about a smell or leak, we don’t just book whichever service you asked for. Send us a photo and a one-line description, and we’ll tell you which service the symptoms point to – including “honestly, a normal $20 servicing will fix this,” which is the answer more often than you’d expect. Our reviews mention this regularly, and it’s the reason customers come back yearly instead of once.
If the technician opens your unit and finds the problem is different from what we quoted – say, a wash was booked but the drain pan is beyond in-place cleaning – we explain it, show you, and let you decide. No work happens that you didn’t agree to.
FAQ
Can I just do a chemical overhaul every time, to be thorough? You can, but you’d be overpaying. A wash already includes a full general service plus coil treatment. The overhaul’s extra cost buys wall removal and component-level cleaning – which only matters when the dirt is in places a wash can’t reach.
Does a chemical wash or overhaul include normal servicing? Both do. You never pay for servicing on top of either – one visit, one price.
How long does each take? Wash: roughly 30–40 minutes per unit. Overhaul: around 45 to 60 minutes per unit, because the fan coil comes off the wall and every part is washed and dried separately. For a 3-unit flat, plan around half a day for an overhaul.
Will an overhaul damage my wall or void my warranty? No to both, when done properly. The fan coil mounts on a bracket designed for removal. We use manufacturer-safe chemicals and re-secure everything on reinstallation – if your original installer left the bracket misaligned, we’ll usually fix that for free while we’re there.
My aircon shows an error code, not a smell or leak. Which service do I need? Possibly neither – error codes usually point to a specific fault (sensor, drainage, refrigerant, PCB) rather than general dirtiness. Check our brand error-code guides on the blog, or WhatsApp us the code and we’ll tell you what it means.
The bottom line
First-time symptom: chemical wash. Returning symptom, old neglected unit, or severe persistent leak: chemical overhaul. Low gas, error codes or drainage installation faults: neither – that’s a different fix, and we’ll point you to the right one.
Still unsure? WhatsApp us a photo of your unit and what it’s doing: +65 8818 5781. We’ll tell you which service you need – and just as importantly, which one you don’t.
Lion City Aircon · 5.0★ on Google across 1,500+ reviews · BizSafe 3 · Serving all of Singapore since 2016. Prices exclude 9% GST.
