Hydrostatic loop

A hydrostatic loop, though not often used in plumbing practice, is an arrangement of pipes formed into a vertical loop to prevent backflow of water within the plumbing potable water system. Since a siphon has a maximum height that it can work, a hydrostatic loop is built higher than 33 feet. There are several ways to prevent siphonage and an undesirable backflow of the water in a plumbing system. The design relies on gravity and atmospheric pressure rather than mechanical devices, making it a passive method of backflow prevention. However, due to its impractical height and space requirements, the hydrostatic loop is rarely used in modern installations, where mechanical backflow preventers or air gaps are preferred.