The #1 water waster in your home is, hands down, the toilet.
A leaking toilet can waste 15,000 gallons of water a month. To check if your toilet has a leak, place several drops of food coloring in the toilet tank. If the color seeps into the toilet bowl within 30 minutes without flushing, your toilet has a leak.
Recently installed toilets use 1.5 to 2 gallons per flush, if you have an older model it can be using up to 8 gallons per flush. Newer models cut total indoor water usage by 30%. And remember to avoid using the toilet as a trashcan.