What is this mistake that can cost you more than 1000 euros per year?

What is this mistake that can cost you more than

Water leaks can cause you a nasty surprise on your bill at the end of the year. For example, a drip wastes about 4 liters/hour, or about €110 per year, a trickle of water can cost you between €400 and more than €1,500 per year, and a leaking toilet flush can cost you up to €700 per year. So it’s time to track down leaks, change the seals and repair your taps. To do this, nothing could be simpler, read your water meter before going to bed, then when you wake up. If the figure has increased, it means you have a leak somewhere. All you have to do is find where and repair it.

lnte1