If nothing in the house is leaking constantly, you should shut off the main water valve in your house. Then open up the water meter box out by the street. You can do this with a pair of pliers. Turn the hexagon shaped nut on the lid until you can pull the cover off. Inside the vault, you will see your water meter. On top of the meter, is a gauge that meters how much water you use. There may be a metal cover over the top of the dials. Lift the lid and you will see a dial, similar to a clock long hand, or a similar measuring dial. In the middle of the face, you will see a triangle shaped, or round, dial that spins when water is moving through the meter. If your main valve inside is shut off and you see this dial spinning at all, it means you have a leak between the meter and the house in the main line somewhere. If your sprinklers are connected in the yard, sometimes water leaks at the tee where the sprinkler line is connected.