Hidden plumbing leaks can waste a significant amount of water and may cause property damage before homeowners realize there is a problem. Common warning signs include an unexplained increase in the water bill, damp areas around walls or floors, low water pressure, running toilets, dripping fixtures, and water-meter movement when every fixture is turned off.A simple household check is to turn off all faucets and water-using appliances, record the water-meter reading, wait approximately 30 minutes, and check it again. A change in the reading may indicate a hidden leak.