Sitting water is the first clue but if you aren’t seeing any visible sign of a slab leak, check your meter first. Your meter is typically located in the front of the building or home in a concrete or metal container. To test the meter, turn off all running water in your building, then check the dial face of the meter for any movement. If you see your triangle or wheel spinning, even with all water off, that indicates a leak. Most commercial water meters have a leak detector to help determine if the water is running through the pipe system.