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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.
Each fixture usually has a characteristic means of connection. Normal plumbing practice is to install a valve on each water supply line before the fixture, and this is most commonly termed a stop or "service valve". The water supply to some fixtures is cold water only (such as water closets and urinals). Most fixtures also have a hot water supply.
It is usually constructed of brass and resembles a 90-degree elbow with a hood on its top to allow air to enter the water system if a siphon attempts to form. Inside this elbow is a poppet valve that is held "up" by the water pressure found in the system, closing the air entrance to the device. If the pressure in the "upstream side" is reduced ...
Also, the tortuous S-shaped path the water is forced to follow offers a significant obstruction to the flow. For high pressure domestic water systems this does not matter, but for low pressure systems where flow rate is important, such as a shower fed by a storage tank, a "stop tap" or, in engineering terms, a "gate valve" is preferred.
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), the dirty water in the sink could be siphoned backwards into the water pipes through the hose and faucet. The dirty water could then be dispersed throughout the drinking water system.
An arctic front moving in will drop temperatures across parts of the U.S. to dangerously low numbers over the next few days.
Some normal water use conditions may cause short episodes of discharge (this is why check one has a minimum passing value of relief +3. It is designed to handle the pressure fluctuations). In the case of the upstream check valve passing, the differential pressure (higher supply pressure compared with the lower chamber pressure) causes any flow ...
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