air gaps
Believe it or not, in our 6th grade health class when we studied about infectious diseases and characters like Typhoid Mary, one of the safety measures shown as well as mentioned in our text book was to hold the fill hose above the water and never let the fill hose fall down into the wringer washer or the wash/rinse tubs while filling them. I guess the book was a little out of date; it was the early 60s, after all, but I had to know why. The teacher explained that if there were a drop in water pressure, admittedly rare and assuredly a huge drop, some of the water from a questionably sanitary situation could be drawn back into the water supply. This would be more of a threat in an apartment building where the pressure on upper floors could be weaker and more likely to be subject to sudden drops if other tenants were to suddenly start using great amounts of water. New outside faucets in our area have to have a vacuum breaker valve, but it's between the normal threaded end the threads onto which the hose is attached.
