leak

We just got a crazy water bill, apparently we've used about twenty times as much water as we normally do in the last three months. Due to the drought, Melbourne has a target for each person to use 155 L of water a day or less. On your water bill, they show how much water you're using in your household, and if you're meeting the 155 L target depending on how many people are in the house. We've always met the target without even trying, but this time we wouldn't be meeting the target even if there were six people living here! They added in an extra note telling us we might have a leak, and how we can check for one. We're doing the test right now, and will email the real estate agent in charge of our house as soon as it's complete. I'm hoping the leak is due to the building that has been going on in our backyard or something else that is obviously someone else's fault. I really don't want to have to pay an $800 water bill when we are used to paying $40!!!