How to Make Water Drain Faster From a Flat Metal Roof

Gain access to the roof either through an access door or by placing a ladder against the side of the structure and climbing onto the roof.

Sweep the roof clear of debris using an industrial broom.

Search the rooftop for any traps or filters covering the roof drains. The traps and filters prevent anything but water from entering the drainage system. If they become clogged, the drainage will slow or stop completely. Put on a pair of work gloves, and then pull away any debris from the traps or filters.

Tap the drainpipes with the head of a rubber-headed mallet to check them for obstructions. A clear drainpipe will sound hollow, while a drainpipe that’s clogged will produce a dull sound when tapped. Remove any filters from the base of the pipes at the exit hole. Place the end of a water hose into the pipe and turn on the water to a brisk flow. Run the water through the pipe to clear any clogs. Turn off the water once the water runs freely through the pipes and test them again.

Dismantle the drainage pipes by using a screwdriver to loosen the couplings and then pulling sections apart if the water does not dislodge the clog. Run pipe cleaners through the sections to push the debris out. Work on a single section at a time, clearing and replacing each, and then test the pipe to determine whether you removed the cause of the drainage problem.