If we have to sum it up in a single rule gutters need a downspout around every 30 to 40 feet.
How many feet of gutter per 3x4 downspout.
With 1 inch per hour 25 mm hr of water to correspond with 1 gpm 0 063 l s flow rate.
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.
The above recommendations assume that you have properly sized downspouts every 40 feet.
The standard is about inch per 10 feet.
Doubling the number of downspouts halves the required capacity for each.
As with gutters a downspout s capacity must match or exceed the expected runoff.
For most homes this means installing spouts at either end of a gutter section.
It is also not as sturdy or durable as metal.
Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.
Many factors can effect the proper size of gutter.
Primary cause for water spillage is debri in the gutter.
The standard is about inch per 10 feet.
Increasing the pitch increases a gutter s handling capacity but the gutter may look askew over a long run.
This downspout has a rust free aluminum construction and a white finish.
For the vast majority of rains gutter and downspouts sizes considerably less than recommended will do the job.
Vinyl tends to become brittle and break in colder climates.
Gutter professionals have experience matching the gutters and the downspouts.
Size downspouts to fit the gutter.
A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.
There are many more important factors that can change this broad rule.
Plumbing codes typically use the vertically projected roof area for drainage design and they often use a square foot allowance per square inch of downspout for 1 in hr 25.
Most of all is location and your average rainfall during a large downpour.
Problems with gutter sizing.
One 3x4 downspout will drain 1200 sq.
Increasing the pitch increases a gutter s handling capacity but the gutter may look askew over a long run.
As with gutters a downspout s capacity must match or exceed the expected runoff.
Downspouts and gutters are sized in relation to rainfall on this basis.
This downspout can be attached with downspout bands not included and is compatible with 3 in.
For example a 6 inch k style gutter requires a 3 x 4 downspout while a 5 inch k style gutter uses a 2 x 3 downspout.
The above recommendations assume that you have properly sized downspouts every 40 feet.
How many downspout installations should your gutters have.