water leak
 

I have a v50 edrive 61 plate estate. Have water coming out of the vent under the drivers seat but only when i have the heater set at "feet" when at other settings all ok.
Putting the a/c on or off makes no difference. Small amount of water in the drivers side foot well and the front passengers side but none in the near side rear passengers.
Have not fully taken up the carpets or taken out the seats as could not see any pipes / vents that would help if any were blocked. Have no sun roof so drainage from that not a problem and all door seals are in good condition.The water is clear water no sign /smell of coolant etc. Any ideas??.