Water dripping - but from where?

[Webskater]

I have a 2012 Toyota Avensis Estate. I have just noticed water dripping underneath the car. On investigation it is dripping out the end of a hose/pipe. Standing in front of the car, if you look to right of the engine - and look right down below the bulkhead, there is a short pipe sticking down. It is open at the end so it must be some sort of overflow arrangement. But there is water dripping out of it all the time. The water temperature of the engine is fine. The level of coolant in the header tank is fine. It doesn't seem to be engine water. It's nowhere near the washer bottle. If you were sitting in the passenger seat, the pipe in question would be in front of, and below, where your feet are. Any idea what this pipe does? Is it anything to do with the heater/air conditioning? 

[mrfixer]

Its the A/C condensate drain pipe. Nothing to worry about.

[matt.evans650]

Yep, its the air con drain, had the same panic wondering what was leaking