Allow 1 square inch of downspout cross-section for every 100 square feet of roof area. Place downspouts at least 20 feet apart but no more than 50 feet apart.
As a general rule, contractors recommend having a downspout per every 20 feet of gutter, but depending on the gutter's capacity, it's not rare to see that distance go as far as 30-50 feet. Large gutters will offer a wider structure to channel more water at a time.
The general rule of thumb is one downspout for every 20-30 feet of gutter. This may vary depending on several factors such as the pitch of your roof, the volume of rainfall in your area, and the capacity of your gutters.
In general, it is recommended that the maximum length of a gutter with a single downspout should not exceed 30 to 40 feet (9 to 12 meters) to ensure proper water drainage. However, this is a general guideline, and it's always best to consult with a professional gutter installer or engineer for your specific situation.
Spacing. There's a rule of thumb that downspouts should be installed at least every 20 feet along the gutter line. However, this can vary based on the factors we've discussed earlier, such as roof size, pitch, and local rainfall intensity.
A maximum 12 m gutter length served by each downpipe is to ensure effective fall and adequate capacity to discharge all water anticipated during a storm having an average recurrence interval of 20 years.
A common guideline is that you need one downspout per 40' span of gutter for proper drainage, but this is usually not enough for a 2”x3” downspout. A homeowner should also consider the size of the roof which will factor into how much water is going into the gutter.
A Elbows guide the water flow in a slight turn, typically used at the top and bottom of downspouts for sidewards redirection. On the other hand, B Elbows offer a sharp, right-angle turn, most commonly used at the downspout base to steer water away from the foundation.
Downspout drains are usually buried from 12 to 48 inches below the ground to better conceal the drainage system.
How far should downspouts extend from the house? 4 to 6 feet from the house but 10 feet if possible. Let's take a look at why this is important, why the slope plays a role, and the different types of downspouts such as extensions, splash blocks, downspout drains, and buried pipes.
To ensure proper coverage and protection, bury your downspout extension at least 12 inches deep. This depth helps protect the pipe from surface activities and ensures efficient water drainage.
Connect the top section of downspout to the bottom section by crimping its edges. A special downspout crimper tool will do this, but you can use needle-nose pliers. Crimp all the way around the downspout to a depth of at least 1 inch. Insert the top crimped section into the lower section as far as it will go.
Size of the Gutter Drainage Area: As a rule of thumb, one downspout should be placed every 25-35 linear feet of guttering. Depending on the local climate and rainfall intensity, some homeowners may need more downspouts. Many homeowners add extra downspouts to boost the drainage capacity of their gutters.
In warmer climates, you can place your hangers close to the center of the gutter, with a spacing of 36 inches in between each hanger. For colder climates, however, you need to space them closer to each other as they need to be able to take the extra load of ice and snow, preferably 18 inches in between each hanger.
Downspouts must also be sized to handle this level of rainfall. Rectangular 2 x 3-inch downspouts have a capacity of 600 square feet, while 3 x 4-inch downspouts can handle 1,200 square feet. Choosing the 3 x 4-inch rectangular downspouts, we'd need at least seven to handle the expected water flow.
The average downspout installation requires two elbows at the top of the downspout and one at the bottom. If you are connecting your downspout into a drain tile, the elbow at the bottom may not be necessary. The standard overhang on a home/building range between 8” and 2'.
The most common angle for downspout elbows for residential gutter systems is 75°.
The major difference is the radius of curvature. Elbow generally have radius of curvature between one to twice the diameter of the pipe. Bends have a radius of curvature more than twice the diameter. Elbows have industrial standards and have limitations to size,bend radius and angle.
Install downspouts every 20 to 50 feet along the gutter. The more closely downspouts are spaced along the gutter, the more water can be conducted away during peak rainstorms.
5” gutters typically get the 2×3” downspout, so be aware that if you add 3×4” downspouts to 5” gutters, it will look very odd. Since work must be done to add your additional, larger downspout, now would be the best time to switch out to 6” gutters, as well.
Your gutters should have a downspout around every 30 to 40 feet. This typically means installing downspouts at both ends of a gutter section.
Fascia brackets should be spaced at a maximum of 1m apart on straight gutter runs. (800mm in the case of the Ogee Gutters, 600mm in the case of the Hi Capacity Gutters). When using 80mm Round Downpipe with Hi-Cap and Ogee Gutters, fascia brackets should be spaced at a maximum of 800mm intervals.
gutter capacity and length. To limit the effects of thermal expansion in gutters 50 ft(15.3 m) is a practical maximum length of gutter to be served by a downspout.
To calculate the minimum number of downpipes, divide the roof catchment area by the allowable maximum catchment per downpipe. To calculate the average catchment per downpipe, divide the roof catchment area by the number of downpipes.