A backflow prevention device including a tank inside of and moveable relative to a housing. A cap coupled to the housing and including inlet and outlet chambers fluidly connected through an inlet, the outlet chamber communicating with the tank. A shell is connected to the cap and includes a shell inlet chamber, which communicates with a first outlet hole of the inlet chamber, and a second outlet hole, which communicates with the tank. An inlet sealing member opens/closes the inlet to fluidly connect/disconnect the inlet chamber and the outlet chamber; and an outlet hole sealing member is moveable with the tank to open/close the second outlet hole. Closing the second outlet hole prevents water from flowing through the second outlet hole and switches the inlet from open to closed. Opening the second outlet hole allows water to flow through the second outlet hole and switches the inlet to open.

An anti-siphon system for use with an irrigation system, such as lawn sprinkling system is disclosed. The system includes a backflow prevention valve with a bonnet- and poppet valve system with a conical spring that biases a lower poppet valve head, and engages the valve body. The use of the conical spring simplifies the mechanism, while providing reliable backflow prevention.

A flushometer valve assembly comprises a flushometer valve body including an outlet, an outlet tube including a conduit extending along a longitudinal axis, and a flushometer valve tube-to-body coupling that directly fastens the outlet tube to the flushometer valve body.

A double check valve is provided that includes an in-line inlet check valve and an outlet check valve that cooperate to prevent back flow of fluid through the valve. The check valve also includes at least one vent that allows for fluid trapped within the check valve to drain, thereby preventing freezing of the check valve and hydrant to which it is interconnected. The check valve provided omits many superfluous components and thus is smaller and easier to install than check valves of the prior art.