Newly renovated house, after the last big rain here in Arizona, we noticed that our sliding glass door let water into the house. It appeared to come into the tracks somehow, but I emptied 5 gallons of water on to the tracks outside and nothing came in. I spoke to a door guy at Home Depot who just so happened to be hanging out and he said he was certain that the issue caused by not having a flashing installed under the sliding glass door.

Does this sound plausible? How would flashing keep water out of the house?

I did notice that our patio got flooded when the water seeped in, but it didn't seem high enough to go up through the track and leak into the house.

[![sliding glass door](https://i.stack.imgur.com/l8LZ6.jpg)](https://i.stack.imgur.com/l8LZ6.jpg)
[![side view](https://i.stack.imgur.com/XFMFc.jpg)](https://i.stack.imgur.com/XFMFc.jpg)