A few weeks ago water started leaking from the A/C units inside my house. I had a company come and clean them but a few days later they started leaking again. What else can I try to do fix the problem?

The drain pipe is probably clogged. If the drain pipe is not clogged you can see water dripping out of it when the A/C is running. Drain pipes can sometimes get clogged easily especially if some small bug/lizard gets caught in the pipe and clogs it. Also make sure the very end of the drain pipe is not blocked.

Also, let's say they thoroughly cleared the drain pipe when cleaning the A/C but did not thoroughly clean the A/C leaving gunk to continue to break off after the cleaning...that gunk can cause a drain pipe clog.

And there is also the possibly your A/C is freezing-up causing an ice sheet on the fins...the ice melts as the A/C runs and drips from the A/C. It also causes the A/C to cool much less since the air flow is blocked by the ice. You can check for icing easily by just looking under the A/C filters. If icing is occurring that usually means you have a refrigerant leak.

The drain pipe is probably clogged. If the drain pipe is not clogged you can see water dripping out of it when the A/C is running. Drain pipes can sometimes get clogged easily especially if some small bug/lizard gets caught in the pipe and clogs it. Also make sure the very end of the drain pipe is not blocked.

Also, let's say they thoroughly cleared the drain pipe when cleaning the A/C but did not thoroughly clean the A/C leaving gunk to continue to break off after the cleaning...that gunk can cause a drain pipe clog.

And there is also the possibly your A/C is freezing-up causing an ice sheet on the fins...the ice melts as the A/C runs and drips from the A/C. It also causes the A/C to cool much less since the air flow is blocked by the ice. You can check for icing easily by just looking under the A/C filters. If icing is occurring that usually means you have a refrigerant leak.

Thank you very much for this useful info. Looks like it was the drain pipe:)

When I installed my aircon I also put a very fine metal gauze over the end of the drain pipe outside to stop things going in such as ants, bugs, jing joks,

On all my Airconditioners I installed a small "U" trap at the end of the discharge pipe so about 5 inches of pipe is always full of water to discourage insects, lizards etc..

This always caused great consternation among the people who regularly came to service the units, virtually every one of them was convinced that retaining water in this way meant that the whole discharge pipe was full of water and so would not function to drain water from the A/C - I had to be extra vigilant when they were around to make sure they did not cur off the "U" trap in an effort to "help" the idiot Farang!

Patrick