Downspout

A downspout's job is to evacuate collected water from the gutter fast enough that the trough never overflows. Standard residential downspouts are 2x3 inch or 3x4 inch rectangular sections (or 3-inch round on half-round gutter systems). The general rule of thumb is one downspout per 20–30 linear feet of gutter for a 5-inch K-style, with 3x4 outlets required when the drainage area exceeds roughly 600 square feet of roof per downspout.

In Sacramento, downspout placement matters as much as sizing. The Sacramento Valley's clay-heavy soils drain poorly, and concentrated downspout discharge at the foundation is one of the leading causes of foundation movement in older homes. Best practice is to extend downspout discharge at least 6 feet from the foundation — either with a surface extension, an underground pop-up emitter system, or a French drain connection.

Downspout components include the outlet (where the gutter feeds into the downspout), elbows to offset around eaves and soffits, straight sections, and a terminal elbow directing water away from the foundation. All connections are riveted or screwed and sealed to prevent leaks at joints.