Big Time Jobs - Downspout

A minimum of one downspout should be used for each 40' of gutter
A 2x3" downspout will handle the water from approximately 600 SQ. FT. of roof area
A 3x4" downspout will handle the water from approximately 1,200 SQ. FT of roof area
A 4x5" downspout will handle the water from approximately 2,000 SQ. FT. of roof area

The seamless gutter industry recommends that single sections of gutter should not exceed 50 FT in length and fasteners should be placed every two feet. Slip Joint Connectors should be used on runs in excess of 50 FT.