What Is a Downspout? And What Is Its Purpose?

Enjoying a rainy day from the comfort of your couch is much easier to do when you know that your house is well protected from the elements. A downspout helps minimize the risk of water damage to your home’s foundation. But what is a downspout? 

Understanding what a downspout is and how it contributes to your gutter system will give you peace of mind—as well as the tools and know-how to keep everything in working order.

This guide offers everything you need to know about this important drainage pipe, including what you can do to maintain it and how it can help you collect water.

What Is a Downspout?

A downspout—also called a waterspout, drainpipe, downpipe, or drain spout—creates a path for water to travel from your gutter to the ground. By creating an enclosed pathway, downspouts help keep rainwater from damaging or eroding your home’s foundation by routing it away from the base of your home.

Without downspouts, water would simply collect in your gutters until it overflowed, gradually wearing away at the structural integrity of your siding, roof, and everything in between. 

Simply put, not having downspouts would defeat the purpose of having gutters in the first place. To create a uniform appearance and boost curb appeal, they’re typically made from the same material as your gutters, like aluminum, zinc, copper, and steel.

What Do Downspouts Do in a Gutter System?

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 of drainage while a 3-inch rectangular downspout can often handle up to 1,200 square feet of drainage.

Let's say each side of your roof measures 40 feet long by 15 feet 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. Stick with 2-by-3-inch downspouts for small gutters and 4-by-5-inch 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. Outsourcing the project to a professional gutter cleaner in your area can cost as little as $119 to take this project off your plate.

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.

Can I Use Downspouts to Collect Water?

If you’re an avid gardener or just want to save money on your water bills, you can collect the water at the end of your gutters into some sort of water collection tank.

One standard solution is a rain barrel. In general, a rain barrel costs about $140, depending on the type of rain barrel and its material. Plastic will be the most affordable material, while stone or ceramic will cost more. 

In addition to the rain barrel itself, you’ll also need to install a downspout diverter. These attach to the end of your downspout and appropriately move the water into your collection tank. Some are even equipped with filtration components that allow you to drink your freshly gathered water as soon as it collects.

Cost to Repair or Replace Damaged Downspouts

The average cost to replace damaged downspouts is about $670 while repairing sections costs about $4 per linear foot. With regular care and maintenance, your gutter system can last anywhere from 20 to 50 years. Considering the average complete gutter replacement cost falls between $1,600 and $2,175 per job, replacing damaged sections rather than installing an entirely new setup will extend the life of your gutters and cost less.

You can save even more money by removing and disposing of your old downspout yourself, which costs an average of $100 per job from a professional gutter installer near you. And doing the entire repair yourself can be less expensive than that.