To find a leak in a hot water tank, check if you can hear a hissing sound coming from the tank. A more accurate method of detection is to disconnect the drain pipe and see if the pressure relief valve is leaking.
To find a leak in a toilet, take off the top of the toilet, and listen for hissing noises. If you hear something, try to find where the noise is coming from. Once you determine the location of the leak, see if you can conduct the repair yourself, or call a plumber. To check if the flapper at the bottom of the tank is leaking, add several drops of food coloring to the water in the tank, leave it for several minutes, and check if the water in the bowl has become colored. If it has, there is a leak that needs to be fixed.
To determine a leak in the meter line, locate the shut-off valve, and shut the water off. Shut-off valves are usually located next to the house. Check if the dial on top of the meter is moving. If it is, there is a leak between the meter and the house, so examine the line closely to find the leak. Sometimes the valve itself can leak.