the 2 slits you see should have 2 slits the same underneath to allow water to drain out of your door frame profile,check this by pouring water into these slits and look at bottom of your frame on the outside,if the water dosnt come out I'd recomend you get some face drain caps from a window company in your area and face drain your frame,if you dont think you can do this yourself ask a freind or family member who works in window trade,if you dont know anyone phone some double glazing repair companies in your area and ask how much they would charge.Hope this helps
shaun www.sdwupvcrepair.co.uk, February 2008