In plumbing, what does 'siphonage' refer to?

Siphonage refers to the loss of trap seal that occurs due to pressure differences in the plumbing system. In a typical plumbing setup, traps are used to hold a small amount of water, which prevents sewer gases from entering the living space. However, if there is a significant pressure change, such as when water is rapidly drained from a nearby fixture or due to the action of a vacuum created in the drainage system, it can cause the water in the trap to be drawn out or siphoned away. This results in an empty trap, which can lead to the unpleasant issue of sewer gases escaping into the home.

Understanding siphonage emphasizes the importance of proper system design to maintain the trap seal. This involves ensuring that venting is adequate to balance pressure changes and prevent siphonage, thus preserving the function of the traps and the overall health of the plumbing system.