Rectangular downspouts move slightly less water at 600 square feet for 2 by 3 inch or 1 200 square feet for a 3 by 4 inch downspout.
Feet of gutter per downspout.
Many factors can effect the proper size of gutter.
The standard is about inch per 10 feet.
For most homes this means installing spouts at either end of a gutter section.
Multiply the number of downspouts by square footage of each.
Installers price gutter systems per linear foot but this price should include all the necessary components for a gutter system including the gutters downspouts the vertical section corner.
Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.
One 3x4 downspout will drain 1200 sq.
A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.
Increasing the pitch increases a gutter s handling capacity but the gutter may look askew over a long run.
For the vast majority of rains gutter and downspouts sizes considerably less than recommended will do the job.
Most of all is location and your average rainfall during a large downpour.
For most homes this means installing spouts at either end of a gutter section.
3200 square feet of roof is calculated as 3200 600 5 33 rounding up you would need 6 2x3 downspouts or 3200 square feet of roof is calculated as 3200 1200 2 67 rounding up you would need 3 3x4 downspouts one 2x3 downspout will drain 600 sq.
Primary cause for water spillage is debri in the gutter.
If we have to sum it up in a single rule gutters need a downspout around every 30 to 40 feet.
The price is the same per linear foot as gutter based on material choice but you may pay more for complementary accessories including hardware hangers drains flashing and splash blocks.
As with gutters a downspout s capacity must match or exceed the expected runoff.
Size downspouts to fit the gutter.
Problems with gutter sizing.
Downspouts prevent your gutters from overflowing experts recommend one downspout for each 30 40 feet of gutter.
For long guttering of 40 feet or more the slope or pitch should begin in the middle diverting the water to a downspout at each end.
Doubling the number of downspouts halves the required capacity for each.
This incline will ensure that water runs downwards sweeping any debris in the gutters toward the downspout outlet.