What is a soil vent pipe?
A soil vent pipe (SVP), also known as a soil stack pipe or a drain-waste-vent (DWV), runs vertically from the underground drainage system to the top of the property, just above roof gutter level. SVPs are typically located externally, however internal SVPs may be fitted inside a property’s outer wall.
SVPs are generally plastic, although many older pipes will have been constructed from cast iron.
How does it work?
The SVP is installed to transport waste from upper floor toilets, baths and sinks into the underground drainage system. However, the vents allow smells and odours from the waste and drainage system to be released into the atmosphere. Placing the outlet at roof level means the odours are dissipated without offending anyone in the vicinity.
The vents also help the process of aerobic sewage digestion by allowing oxygen into the system.