Water UK reported that 700,255 properties experienced unplanned interruptions in excess of six hours, up from 119,880 in 2009/10.
Exceptionally severe winter weather was blamed for the soaring figures, as freezing conditions led to high numbers of burst pipes.
Northern Ireland was by far the worst hit, with 60 per cent of customers affected, compared to 3 per cent for the second worst.
Water UK’s full sustainability report can be found here: http://bit.ly/wvP5Me