Earlier, a group of City Hall refuse truck workers who happened to be collecting rubbish at the nearby communal bin noticed the man standing near the water tank and later climbing up the ladder.
They saw the man reach the top but later disappeared.
A team of firemen arrived shortly and one of them jumped into the water tank to retrieve the wet and visibly shaken man.
There was an all round applause from the crowd who had gathered at the scene when the man was rescued and brought to a waiting Civil Defense ambulance. He was taken to the Queen Elizabeth Hospital II.