A small leak (1/32 of an inch) can waste 170 gallons in 24 hours. This can add up quickly. Make sure to fix leaks as soon as possible, if you are unable to repair or diagnose them, you may want to call a licensed plumber.
How to Detect Leaks in Home
Read the water meter in your basement before going to bed or work, then read it again when you get up or get home. As long as you know nobody used water, the softener hasn't cycled, etc., the meter dials won't move.
Most leaks in a home are related to the toilet. Make sure the toilets are in proper working order. If you have to jiggle the handle to get the water to stop, this is a sure sign that repairs need to be made.