The water line running to your home is "metered" (measures consumption in thousands of gallons) for accountability and billing purposes. A leak on your line can be very costly, no matter how small it may be. View some of the areas you can check when looking for a leak:
Movement on Meter
Your water meter has a “leak detector” on it in the shape of a little red triangle. When in motion, even the slightest of movement, that is indicating water being used. If you know you are not using water, (not washing clothes, showering, ice maker is off, etc.) and the leak detector shows movement, then you have a leak. You can try to isolate the location of that leak into two areas: within the house or between the house and the meter.
What to Do
The first thing to do is to go out to your house valve (usually located below your hose spigot) and turn it off. Now go check the leak detector on your meter.
Leak within your house: If it has stopped moving, then the leak is somewhere within your house
Leak from the house to the meter: If it is still moving, the leak is somewhere between the house and the meter and not inside your house
Check the toilet for a leak by first shutting off the water valve underneath the toilet. Remove the top off the tank and mark the water line with a pencil. Do not use the toilet for two hours. Come back and check the water line. If the water level has dropped lower, then you have a leak in that toilet. Repeat this process for each toilet in the house.
Check all faucets, hose connections, and shower heads for any drips. A drip is small but it can cost you big on water usage fees.
Check the water level in your pool. If you need to fill it often, there could be a leak.