If your water bill shows an unexpected jump, check for leaks. Toilets are the number one cause of lost water in homes. Make sure the water level in the toilet tank is roughly half an inch below the top of the overflow tube. The rubber flapper valve could also be leaking. A great way to check would be to pour any colored liquid such as food dye or even a cup of coffee into the back tank of the toilet. Let it stand unflushed for ten minutes and then look inside the bowl. If any of the colored water seeped into the toilet bowl, then the flapper is bad and needs to be replaced. This is a very inexpensive part that can save you hundreds of dollars in lost water.