Hi I've bought a new house and i have a upvc door fitted with a low threshold and every time it rains its leaking through the inside. Anyone knows what to do. Ive poured water on the door and it seem like its only leaking from underneath. I had a quick look at the rubber that slots in under the door and seems ok. Does anyone know where i can find this seal from also there doesn't appear to be any drain holes in the threshold im not sure if its meant to have it. Thanks.