This Maestrini siphon break valve is made from brass. It is used to operate anti-siphon loops typically on board boats where equipment is installed below the waterline, such as engine intakes, wet exhausts and marine toilet systems.

Can be used in conjunction with BSP plumbing fittings to make an anti-siphon device, for example a 407105 1" BSP T piece, two 407045 BSP elbows and then two hose tails to connect the hose (404054, 404057). Larger sizes can also be made, by using adaptor bushings with larger T pieces.