: what is the vacuum breaker for an outside faucet

Reply:
It is to prevent backflow from the garden hose into the domestic water piping. Let's say if there is a garden hose laying in a puddle of filthy stagnant water and there is the situation that occurs which a pipe breaks inside the house or in the street main, it is possible for a backflow of that filthy water to be siphoned into the garden hose and then into the household water distribution system (possibly without anyone knowing it). A vacuum breaker will stop the backflow and spill it out onto the floor or ground.
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• http://edis.ifas.ufl.edu/AE079