Sometimes rain gutters overflow, but if it happens too often, consider more drainage. Today you'll learn: if overflow is drenching you, instead of one downspout...you may need two! The remedy for gutters that ?runneth over? is usually just a good cleaning (removing obstructions like leaves and debris.) But if a good downpour still overwhelms your rain-carrying system, some re-engineering may be in order. A single 2x3-inch downspout can handle runoff from 600 square feet of roof. A single 3x4-inch downspout can handle twice that--runoff from 1200 square feet of roof area. For larger roofs, or gutters that regularly overflow, a second downspout may be in order. For new construction and gutter replacement, always temper roof and downspout analysis with rainfall intensity in your neck of the woods. It's also better to over-accommodate ?drain-wise? than to endure ?overflow? rain-wise. One downspout or two? Think it through!