Which plumbing system is required to have venting to prevent suction when draining?

The drainage system is required to have venting to prevent suction when draining. Venting is essential in a drainage system because it allows air to enter the piping system as wastewater flows out. This action helps to equalize pressure within the pipes, preventing any potential vacuum or siphoning effect that could disrupt the flow of waste. If there is no proper venting, a negative pressure can form, which may lead to slow drainage, gurgling noises, or even the potential for traps to be emptied, resulting in sewer gases entering the living space.

The water supply system does not require venting in the same manner, as it typically operates under positive pressure and is designed to deliver water rather than drain it. The sewer system, while related, primarily deals with the conveyance of wastewater to a treatment facility, and venting principles apply to drainage systems specifically. The recycling system, depending on its design, usually focuses on reclaiming wastewater without the same venting needs as a drainage system. Thus, proper venting is a critical aspect of the drainage system, ensuring efficient and safe wastewater disposal.