“For maximum effectiveness, use 4-inch perforated PVC pipe,” says Lamprey. PVC lasts longer, and if you encounter a clog, it can be cleaned with a pressure washer or plumber’s snake.

Water passing through the soil would discover this gravel, immediately drop down through it to the perforated drain pipe and then exit to daylight, never having a chance to enter the garage.

I only use perforated PVC pipe for drainage applications because it's durable, flushable and it maintains proper slope underground. Any other type of drain pipe is unreliable and problematic.

Install the filter sleeve on the perforated pipe, if it didn’t come pre-installed. Then lay the drain pipe in the bottom of the lined trench. Backfill the remainder with clean drainage gravel.