A downpipe carries rainwater from gutters to drainage. It is a vertical pipe attached to the side of a building. The gutter collects water from the roof. The downpipe channels it to the ground, where it flows into a storm drain, a dry well, or a rainwater harvesting system. Without a downpipe, water would pour off the roof and erode the soil, damage the foundation, and stain the walls. The downpipe is a simple but essential part of a building's water management.

Downpipes come in several materials. PVC is cheap, light, and easy to install. Aluminum is lightweight and corrosion-resistant. Copper is durable and develops a patina over time. Cast iron is heavy and long-lasting, used in historic buildings. Steel is strong but requires painting. The material affects the look, the cost, and the lifespan. The pipe is sized based on the roof area and the rainfall intensity. Too small, and it overflows. Too large, and it is wasteful.

Downpipes need maintenance. Leaves and debris can clog the gutter or the pipe. Ice can block the flow in winter. The pipe can leak at the joints or crack from freezing. A blocked downpipe can cause water to back up under the roof, leading to rot and mold. Regular cleaning and inspection prevent problems. The downpipe is not glamorous. It is hidden in plain sight on the side of every building. It works silently. It protects the structure. It is one of the unsung heroes of construction.