Hydrostatic loop

For closed or open loop hydraulic systems, see Hydraulic machinery.

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 (about 33 feet), 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.^[1] 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.

• Vented loops ^[2]