The benefits of a plastic downspout are its flexibility, durability, and the ease with which it can be cleaned. The negative aspects of a plastic downspout appear when too thin a material is chosen. This can create clogs and cause water to backflow into the home.
Many types of plastic PVC piping are available that can be used as downspout piping. They are offered in a variety of thicknesses and may be smooth or ridged. Smooth plastic piping typically allows for the easy passage of water, small bits of debris, and downspout cleaner. Ridged plastic downspouts may cause debris to catch on the interior of the pipe, which can impede water flow. These types of pipes also do not usually work with certain types of downspout cleaner.
Plastic downspout piping is available with and without perforations. These are small holes or openings that run the length of the piping. Perforated PVC piping, when used in underground downspouts, allows water that stands within the piping to drain into the ground. This type is typically only used in well-drained soil.
Plastic downspout piping does not rust over time, and is more easily repaired than other kinds of spouts. These characteristics are preferable to various types of metal downspouts, as its purpose is to transport large amounts of rain water away from the home, and water can cause metals to degrade. For instance, steel and other metals will rust over time and must be replaced periodically. Also, they often stain the exterior of the home. Plastic does not rust or stain, and a patching material that can be used to mend holes in plastic downspout piping is generally available at most home improvement stores.
Durable, plastic piping often lasts the lifetime of the structure. When choosing a plastic PVC material to use as downspout material, carefully select a type with a thick wall. This piping is often installed on the exterior of the home to allow rainwater to drain from roof gutters down into the yard.
Thin plastic piping does not perform well when buried as it will not withstand heavy amounts of dirt placed on top of it. It can also clog easily and allow tree roots to penetrate its surface, which can, over time, prevent the flow of water entirely. Thin piping should also not be used as an underground downspout, but is sufficient to run along the exterior of the house.