Frightening isn't it.  Have you checked the service charges?  Are you sure it's the water that has caused the problem?

Once the test was done it worked out to about 4 ltrs a minute , thats a lot of water . From the looks of it from work been done  the leak was in the driveway which runs down the middle of units ( 3 on each side ) but wasnt visable . They fixed this same area just before xmas ..obviously not properly .

If you're renting you can only be charged for water if your place has its own meter.