the gap between the bottom of the tap and the highest water level in a sink wash basin or bath
Stephen Baguley, April 2010
If you didn't have this air-gap, back-siphonage could occur - i.e. dirty contaminated water from a sink could be sucked back into the mains. It is a requirement of water bye-laws etc.
JD, October 2008
an air gap in the gap between the overflow or the spill over level off the bath,basin,sink etc and the outlet (tap).
wullie (carlsberg) plumber, October 2008
I agree with froddos answer.
ring a plumber and try not to touch anything else in your house containing water/gas/electricity. please!
