This is not a major problem and simple for the air conditioning people to sort out. All that is needed is for a small vent to be inserted into the drain pipe just behind the offending unit. the vent which is a small piece of plastic and costs about 1 euro, is there to allow the pipe to breath when it gets full of water, otherwise a vacuum is created and the water will not flow away.
Contact Appollo Air Con or anybody else who knows their way around a unit and they will fix it immediately. Don't bother with Polaris or any build guarentee stuff - waste of your time and you will get old before it is sorted.
Jon Faulkner