I'm in a block of flats and only the cold water in the bathroom taps and toilet have trickled to a halt. Whilst the cold water in the kitchen runs freely, there is none in the bathroom. The plumber said it is an airlock which he said he cleared. However, one day later the problem has reocurred. Is this an airlock problem or is it something else?

LWhat did the plumber do to clear the cold water lines?