Water Supply & Distribution第 47 / 120 题
Which condition makes a pressure vacuum breaker an unacceptable choice for a given cross-connection?
a.The outlet is a hose thread connection
b.The device would be located outdoors
c.The supply piping is copper rather than steel
d.A booster pump downstream could push water back toward the supply
解析
A pressure vacuum breaker protects only against back-siphonage; a downstream pump creates back-pressure, which requires a double check assembly or reduced pressure assembly depending on the hazard level. Hose thread outlets, outdoor locations, and copper supply piping do not disqualify a pressure vacuum breaker. The distinction to remember is back-siphonage (negative supply pressure) versus back-pressure (higher downstream pressure).
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