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.
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.
The number of downspouts needed depends on the length of your gutter system and the volume of rainwater in your area. As a general rule, you should have a downspout every 20 to 30 feet.
To get the best draining results from your gutters, we recommend having at least one downspout for 50 feet, and two 2 downspouts for over 50 feet.
Typically, residential downspouts come in two sizes: 2x3 inches and 3x4 inches. The former is often used for smaller roofs, while the latter is preferred for larger homes. A 2x3 inch downspout can handle roughly 600 square feet of roof area for every inch of rainfall within an hour.
If we have to sum it up in a single rule, gutters need a downspout around every 30 to 40 feet. For most homes, this means installing spouts at either end of a gutter section.
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.
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.
5 inches and 6 inches gutters are the most common sizes installed for residential use. However, 7, and 8 inches are available although the larger sizes are more suitable for larger buildings or business properties. As far as downspouts go, they run at 2″x3″ and 3″x4″ in size or 3 or 4 inches in diameter.
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.
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.
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.
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.
A properly installed underground downspout extension consists of an upright PVC pipe that runs into an elbow joint below ground with another length of pipe, at least ten feet long, extending underground away from the house.
The most common angle for downspout elbows for residential gutter systems is 75°.
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.
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.
Even though 68mm round and 65mm square downpipes are among the most common, most rainwater systems are available in multiple sizes. For example, this might be 75mm, 87mm, 100mm and 120mm for a certain range, with corresponding gutter sizes to match.
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.
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.
6 Inch Gutters Hold 50% More Water Than 5 Inch Gutters
It will also protect plants below the guttering and prevent channels from forming after rainfall.
Standard downspouts can run at 2x3 inches or 3x4 inches, which is what fits most residential gutter profiles. A downspout can also be as wide as 6x6 inches, but downspout sizes larger than 4x4 inches in diameter are only paired with gutters and buildings that also exceed the average in terms of size.
Gutters and downspouts shall have a slope of not less than 1/8 inch per foot (10.4 mm/m) along their entire length. Gutters and downspouts shall be installed so that water does not pool at any point.
Poor Positioning. The golden rule for positioning your rain gutters is that they should always be placed about three inches below your roofline. The reason being: if they are placed too high, they can allow runoff water to spill out over their backside.