Scupper drains are the best way to remove water off a flat roof. Installing a scupper drain is simple and costs less than other drains. Scuppers don’t clog as easily as inner drains on a flat roof. Normally the debris and leaves get washed off through a scupper with a rainstorm. Scupper drains almost always will drain water of a flat roof, unlike inner drains that have strainers that get clogged.