Spray the door and look for the leak location.
Patio door leaking at top.
Aim a garden water hose with a sprayer set on mist or low at the outside of the sliding door.
Have a reputable sliding door contractor remove the door if it has not been damaged build a new frame and reinstall the door.
Water leaking through patio door.
Door bottoms seal between the panel and door sill so watch for signs when your door bottom needs replacing.
Door bottoms are important but leaks can also be caused by the door sill.
Causes of door leaks there are many potential pathways for water to leak in through a door but the biggest opening is of course the doorway itself.
Even brand new door bottoms won t create a secure seal if your door sill isn t properly adjusted.
We ve tried everything much like eric above including getting the balcony refelted and new patio tiles put on we ve also put a lip around the balcony.
Damage to the door itself.
If a frame is crooked water can leak into the gaps between door and frame.
There are patio doors to the balcony and the leak comes in under the wooden frame of the patio doors the doors are plastic and soaks the carpet and woodwork.
A sliding glass door is no better than the frame into which it is placed.
I plan to seal.
I ve got a sliding patio door on the back of my home there s a moisture problem directly under the door in the basement.
If you cannot re create the leak problem inspect the interior of the door for stains or rust.
It may seem obvious but a door left open or one that cannot be closed tightly because of wear and tear is a significant problem during a storm.