air lock, or water turned off, try holdind the palm of your hand up very tight to the outlet of the mixer tap, turn on the cold water tap all the way,open it" now turn on hot tap, but dont have the hot water on, you will need a towel or tea cloth near, to hold down the spray, what your trying to do is force the hot water back up into the cold water tap, to shift the airlock out of the cold water pipe, you will need to do it for 2 to 3 mins, to move the blocked air, there will be water spraying around, thats why you need a towel over the mixer, but if its airlocked this will shift it , and the cold water will run again,,
k, January 2012
