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An anti-siphon valve is also required here to prevent pressure drops in the water supply line from suctioning water out of the toilet tank (which may contain additives such as "toilet blue" [53]) and contaminating the water system. Anti-siphon valves function as a one-direction check valve. Anti-siphon valves are also used medically.
Toward the end of the discharge process, the ballcock responds to the drop in water level and refills the tank. Should the float or valve fail and allow the water level to exceed the fill line, the water will pour into the overflow tube and out to the bowl (in the flapper valve type) or to an outside drain (in the siphon type).
Backflow prevention device. The simplest, most reliable way to provide backflow prevention is to provide an air gap.An air gap is simply an open vertical space between any device that connects to a plumbing system (like a valve or faucet) and any place where contaminated water can collect or pool.
If the pressure in the "upstream side" is reduced to atmospheric pressure or below, the poppet valve drops and allows air to enter the system, breaking the siphon. [1] One-Inch Brass Atmospheric Vacuum Breaker mounted on PVC Pipe. These devices, since they work on atmospheric principles, cannot be installed in an enclosure containing air ...
The siphon is formed of a vertical pipe (1) that links the flush pipe (2) to a domed chamber (3). A perforated disc (4) covered by a flexible plate or flap (5) is joined by the siphon rod (6) to the flush lever. Pressing the lever raises the plate, forces water over the top of the siphon into the vertical pipe, and starts the siphonic discharge.
A vacuum breaker is a device that prevents water from being siphoned backward in a direction it is not desired to go. They are commonly placed on a bibcock valve or toilet or urinal flush valve, in which application they can prevent hose or drainage water from back-siphoning into the public drinking water system.
To further illustrate the air gap, consider what could happen if the air gap were eliminated by attaching a hose to the faucet and lowering the hose into a sink full of contaminated water. Under the right conditions (if the water supply loses pressure and the sink is higher than the point at which the water supply enters the house, for instance ...
Air admittance valves (AAVs, or commonly referred to in the UK as Durgo valves and in the US as Studor vents and Sure-Vent®) are negative-pressure-activated, one-way mechanical valves, used in a plumbing or drainage venting system to eliminate the need for conventional pipe venting and roof penetrations.