The first thing you should do is to locate the water meter. After that, there are a few steps that you should follow for accurate readings:
1. Make sure that no water is used inside the house.
2. On your meter you should probably have a flow indicator. This is a small red triangle that is rotating when water is flowing. If there is no water usage in the house, but the meter is still turning, or it has changed position during inspection time (usually 1-2 hours) than this is an indicator that you have a leak.
After that you have established that you have a leak it is time to check if the leak is located inside the house or in the outside plumbing coming from the meter to the house. To check if the leak is on the outside simply close the main valve that leads into your house. If the meter is still turning than the leak is on the outside plumbing. To check roughly where the leak is, follow some simple clues such as greener grass than the surrounding area, faster growing grass or muddy wet patches. This will give you an idea of where the leak may be and to help you guide the plumber to the exact place. If the meter is not turning after the main shutoff valve is closed (but was turning before) this means that the leak is somewhere in the house. You should use a methodical approach to detect the leak, checking the most common places for leak occurrence.
Leaking faucets – The most common cause for leaking faucets is the worn rubber seal on the handle. This is easy to be replaced, if you have the right tools. Before attempting the repair make sure that the main shutoff valve or the valve beneath the sink is closed. The lever of the faucet is not a shutoff valve.
Leaking toilets – This is the most common leak inside the house and even a small and silent leak can cause hundreds of litters of wasted water which will show up on your bill. To determine if the toilet is leaking, simply lift the cover of the tank and put a few drops of food colouring inside. Check the toilet bowl after few hours to see if the colour is present. If there is colour in the bowl than the leak can be caused by several factors which are worn rubber seal on the flapper or the filling mechanism. This is an easy and cheap fix that can save you money.
Pressure valve release – This valve is located on the water heater and if it is not functioning correctly it can begin dripping and water may accumulate on the floor. Often this valve is connected to a water outlet. If so listen carefully for a hissing sound that will indicate a pressure valve leak.
The water you drink and bathe with is delivered under pressure, so a leak can be very obvious. Wastewater, on the other hand, is usually moved by gravity and is not under pressure. This makes wastewater leaks much harder to detect.