Aircond dripping inside the house: the blocked drain pipe behind most 'leaks'

Short answer: when an aircond drips inside the room, it is almost never a refrigerant leak. Refrigerant is a gas; it does not puddle on your floor. What you are seeing is condensate, the water the indoor unit pulls out of humid Serdang air every minute it runs, failing to get out through its drain pipe. In most houses around Seri Kembangan, Balakong and Kajang the drain is blocked with grey slime, or it was installed with a sag that traps water, and both are fixable without touching the gas side at all.

Where the water is supposed to go

Below the cold coil in the indoor unit sits a plastic tray. Water runs off the coil into the tray, out through a small outlet, into a soft drain hose that leaves the wall with the copper pipes inside the white trunking, and on to a PVC pipe ending outside, usually over the porch or into a bathroom pipe. On a hot afternoon a bedroom unit sheds over a litre an hour, so once that path is blocked the tray overflows at its lowest edge. That is the drip you see.

A ten-minute check before you call anyone

Run the unit at a low temperature for twenty minutes and go outside to where the drain pipe ends. It should be dripping steadily. If the room is cooling but nothing comes out, the drain is blocked. That is your diagnosis.
Switch off at the isolator and open the front panel. If the filters are grey with dust, wash them. A choked filter starves the coil of airflow, the coil freezes, and the ice sheet melts in a rush when the unit cycles off, which overwhelms a perfectly healthy drain.
Look at the copper pipe where it leaves the unit. If the black foam insulation has perished, the cold pipe itself sweats in our humidity and drips from the trunking, not from the unit. That is a re-insulation job.

Clearing the drain yourself

The slime is a biofilm that grows in the standing water of the drain line. It loves a pipe that never fully empties. If the outside end is reachable, a wet-and-dry vacuum sealed over it with a rag pulls the plug out in seconds. No vacuum? Pour clean water slowly into the tray with the unit off and watch for it outside; if it backs up, work flexible wire or a drain brush into the outside end. Avoid blowing compressed air inwards towards the unit; it pushes slime into the tray outlet and the unit floods the next day.

Once it is flowing, pour a cup of diluted bleach or a drain-line tablet through the tray every few months. That is honestly all the maintenance the line needs.

When it keeps coming back: the installation is wrong

Aircond cleaners rarely mention this because it is not their trade. Water only moves downhill. If the drain pipe was run along the ceiling void or down a long wall with a belly in it, water sits in that low point permanently, slime grows there, and no amount of chemical washing cures it for more than a month or two. The same happens when an installer teed the drain into a bathroom waste pipe without a trap: the unit gurgles when the toilet flushes and the bedroom smells faintly of drain because sewer air travels back up the hose. Both need a drain re-route, which is handyman work, not an aircond service.

What you see	Likely cause	Who fixes it
Drip from the unit, nothing coming out the outside pipe	Blocked drain line	DIY first; aircond service if you prefer
Drip only after hours of running, ice on the coil	Dirty filter or low gas	Wash filter; gas is an aircond technician’s job
Drip from the trunking, not the unit	Perished pipe insulation	Handyman re-insulation
Gurgling, smell, recurs every few weeks	Drain sagging or teed into bathroom waste	Handyman re-route, RM 100–500 plumbing range
Brown ring on the plaster ceiling below the pipe run	Drain leaking into the ceiling void	Fix drain, then patch or replace the board

The damage you do not see

In double-storey terraces the drain often runs through the ceiling void of the room below. A slow drip up there never shows at the unit; it shows as a brown ring spreading on the gypsum board downstairs, sometimes weeks later. Press the stain gently: if it is soft, the board must be cut out, not just painted. On the wall side, repeated overflow soaks the plaster behind the unit and the paint bubbles off a year later.

What we do and what we do not

We are not aircond gas technicians. If the coil is icing with clean filters, you need someone who can check refrigerant pressure, and we will say so. What we do take on is the building side: re-running a sagging drain with proper fall, moving a drain out of a bathroom waste pipe and giving it its own outlet, re-insulating a sweating pipe run, and making good the stained ceiling or wall afterwards, usually in one visit. See our services and the price guide for what that typically costs. If the twenty-minute test shows water flowing outside and the drip stops once the filter is clean, you have already fixed it, and you did not need us.