Drainage



Drainage is another common issue in skyscrapers, and is often just as difficult to solve as water pressure problems. When water falls vertically down a pipe, the water will adhere to the pipe's walls until the pipe's cross sectional area is about one-fourth full. Once the gravity propelled water hits a horizontal bend in the pipe, the flow velocity drops dramatically, and fills the pipe considerably more due to the lost speed. It is common practice to use relief or yoke vents to slow the water before it encounters a horizontal flow change. The piping at the base of a vertical drainage column must be secured, as to reduce the risk of breaking joints.



Venting
For water to travel down a vertical pipe, air is necessary. Air ventilation must be controlled so that low pressure zones can be created, and the flow of water can continue. The low pressure zones should not be placed near a fixture, or else poor drainage could occur (often recognized by a gulping sound and poor flow performance). It is however okay to place air vents in the fixtures themselves to increase water flow.
Material

Most high-rise plumbing systems use Type-L copper. On some very tall buildings, stainless steel must be used because of the extra pressure.