Downspout pieces are straight ten foot sections. There are some cases where it is necessary to adjust the direction that a down spout flows. It is very rare that the downspout can come directly out of the gutter and straight to the bottom of your house without having to change direction. The fact that the downspout might not be right next to the house, obstructions blocking the path of your downspouts, or your desire to redirect your gutter water to a barrel or storm drain are all reasons to use gutter elbows.
Since gutters are attached to the eaves of your roof and your roof might extend out away from the side of the house, you usually cannot just have the downspouts go straight down from the gutters. The weight of the water flowing through them would make the gutter and the downspout separate if there was not a way to attach the downspouts to the house. In order to get the downspouts over to your siding you need to use an elbow. Elbows change the direction of the downspout forty five degrees. You can attach an elbow to the gutter attachment and angle back towards the house. Then you can use a small extension piece to reach the house. Another elbow will angle downward where you can attach the long downspout pieces.
It is possible that there is a lip or section of the house that is farther out than the rest of the house. If this is the case, you will need to angle around it or out to meet it. Short elbow pieces can make a tight turn and shift your downspout out or in only a few inches.
The other place that elbows come in handy is at the bottom or discharge area of the downspout. You never want to let your downspout empty right onto the ground next to your home’s foundation. There are a number of problems that can be caused by too much water in the soil next to your house. Improper or too infrequent gutter cleaning can be one way that water problems crop up, but a poor downspout design can also be the reason. There are special show shape gutter elbows that are meant to be used at the bottom of a downspout. The elbow angle out away from the house and a long straight piece carries the water a safe distance away from the foundation.