As you can tell, downspouts play a very important role in a gutter system and should be a key factor when planning how to install gutters.

The gutter and downspout connect just above the fascia board—the piece of wood that sits between the bottom of the roof and the top of the gutters. Without a downspout, the fascia board will be the first part of your home to suffer from water damage.

Before you can attach a downspout to your drainage system, you must first insert a connecting pipe via a hole in the gutter. Then seal the hole shut to prevent leaks and attach the top of the downspout to the connecting piece with either glue or screws. From there, the rest of the pipe is fixed all the way down the side of the building until it meets the ground.

The downspout is curved at both the top and bottom to better catch and dispense water, but this isn’t always enough to ensure that water doesn’t pool at the base of your home.

Depending on your surrounding landscape, you may need to install a downspout extension pipe or bury your downspout underground to ensure that excess water is diverted from your home.

How Many Downspouts Do I Need?

 In general, your home will need about one downspout for every 40-foot run of gutter. However, a typical square or rectangle-shaped home will need one downspout at the end of each gutter, meaning a downspout on every corner of the home.

One way to calculate how many downspouts your home needs is to figure out the drainage area of your roof, or the amount of roof surface a gutter and downspout will be responsible for. For a simple gable-end roof, with two sides, you multiply the length by the width of each side of the roof to get the drainage area of each side

The size and shape of the downspout will also impact the number you need. The larger the downspout, the more roof it can handle. A 2-inch rectangular downspout can handle about 600 square feet(55.5 square meter) of drainage while a 3-inch rectangular downspout can often handle up to 1,200 square feet(111 square meter) of drainage.

Let's say each side of your roof measures 40 feet(3.7 meter) long by 15 feet(1.39 meter) high. That gives you a drainage area of 600 square feet per side. You'll need at least two 2-inch rectangular downspouts on the roof.

Things get more complicated with more complex roofs, such as hip roofs, with four sides, or roofs with multiple levels. If you have a complex roof, calculate how many downspouts you need by determining the drainage area of each section of your roof.

It's not only the roof size that matters. A few other factors also influence the number of downspouts your home needs:

• The pitch of your roof: The steeper the pitch, the more downspouts you need, as water moves more quickly down a steep slope.
• The amount of rainfall in your area: If you live in an area that experiences heavy rainfall, you may want to add more downspouts than average to accommodate the extra water.
• The size of your gutters: The bigger your gutters, the more water they can handle without becoming overwhelmed. If your gutters are on the small side, such as five inches, you may want to add an extra downspout to help them drain more efficiently. 

What Are Standard Gutter Downspout Sizes?

The size of your downspouts will depend on how large your gutters are. The most common gutter sizes range from 5 to 8 inches(12.7 cm to 20.32 cm). Stick with 2-by-3-inch (5.08cm to 7.62cm) downspouts for small gutters and 4-by-5-inch (10.16cm to 12.7cm) downspouts for larger ones.

Can You Extend Gutter Downspouts?

If your downspouts are routing water too close to your home’s foundation and pooling water in no-swim zones, you can extend your gutter downspouts. It’s a relatively simple DIY project that can make a pretty significant impact if you’re concerned about water pooling and leading to other issues like foundation cracks or flooded landscaping.

Some of the most common extension options include plastic or concrete splash blocks or aluminum or plastic extenders that attach to the end of your downspout.

How Often Do Downspouts Need to Be Cleaned?

The good news is that you only need to complete downspout cleaning about once or twice a year, which just so happens to be the same amount of cleaning sessions your gutters need, too. If they’re not draining properly or are full of debris, it’s time for some TLC.

Cleaning your gutter system can be done with a few common household items, like a bucket and a ladder—and a bit of willpower. But it’s not as easy as your typical chore.

Should I Bury My Downspouts?

Burying your downspouts is a good idea if water doesn’t distribute evenly over your lawn or it frequently rains where you live. Doing this involves a bit of work, like mapping a route for your downspout extension and digging a trench, but the results will be worth it if you’re tired of struggling with a faulty drainage system or repeatedly having to unclog your downspouts.

Conclusion

The downspout is a small but vital component of a home's defense against water damage. Acting as an essential enclosed pathway, it works with your gutters to effectively channel rainwater away from your foundation, roof, and siding, thereby preventing erosion and preserving your home's structural integrity. Ensuring you have the correct number and size of downspouts for your home's roof pitch and local rainfall is crucial for proper drainage. Finally, by committing to simple, regular maintenance—such as cleaning them once or twice a year—you can ensure your downspouts function correctly, providing you with the peace of mind that your home is well-protected from the elements.