Why Is My Panasonic Aircon Leaking Water After Long Runs?

A fully blocked drain floods within the hour, every time the unit runs. A timed drip does not behave like that. Water still leaves the tray. It just leaves more slowly than the coil fills it.

That is a race between two rates, and the tray is the buffer sitting between them. On a short run the drain keeps up. On a long run the level climbs past the lip and spills over.

This is why the unit still cools while it drips. It is also why the leak feels random, and why a quick on-off test in front of a technician shows nothing wrong at all.

Note the run length before the first drop, then match it below. Timing does more work here than the spot the water lands on.

A leak that takes hours to appear is a restriction rather than a break. The length of the run says how far down the route it sits.

A leak that only follows a full night is often not drain water at all. The water tracks along the trunking instead of the unit.

There is also a stage before the drip. A pan that drains too slowly holds water between cycles, and the room smells musty at start-up while the cooling stays fine. Nothing has overflowed yet. The line is already narrowing, and flushing it then is cheaper than flushing it after a ceiling stains.

Trunking carries cold pipe, drain pipe and cable inside one cover. Two of those can wet a wall, so a damp seam settles nothing on its own.

The common one is sweat. Where insulation on the cold pipe has opened up, humid room air reaches bare metal and condenses on it. That water collects inside the cover and tracks down until it finds a seam.

Sweat has a signature. It needs a long cold soak to form, so it follows a full night and never a short session. The mark also starts away from the unit casing, at the point where the gap sits.

Drain water behaves differently. It backs up first, then escapes at a joint or a low point, and it follows cooling load rather than pure runtime. Opening the cover at the wet section separates the two in a minute. That should happen before anyone quotes a new drain line.

The distinction decides the repair. Fit a new drain line to cure a sweating pipe and the damp patch survives the work, along with the bill. Sealing the insulation, then rechecking the drain before the cover goes back, is the proportionate job.

A leak that returns after the line was flushed is usually about the shape of the route, not what is sitting inside it.

Flushing removes debris and leaves the geometry untouched. A section sloping the wrong way holds water however clean the pipe is, and it fills again on the next long run.

Reverse slope turns up most in retrofitted trunking. A drain fitted around an existing building takes awkward turns, and one of them ends up level or falling backwards. Long runs, tight bends and flat stretches all raise the odds.

The same rule governs a new installation. Condensate moves only while the pipe keeps falling, the whole way, with no exceptions anywhere along it. A beam overhead costs the line its fall. Recovering that fall elsewhere is harder than routing around the beam, so the route gets levelled end to end before the ceiling closes.

Photograph the mark before wiping it. Where a stain starts, not where it ends, shows a technician which section gave way.

Kill power at the isolator if the water is tracking toward a light fitting, a socket, or a void above a ceiling. Nothing else here is urgent. Condensate is room moisture, not refrigerant, and it forms on the outside of sealed pipework.

Then keep it switched off. More cooling means more water arriving at a route that already cannot clear it, and a larger stain to explain later.

Question any quote that opens with a tray, a coil or a full drain replacement. A flow test along the whole route, under a real cooling load, takes minutes and is what shows whether those parts are involved at all.