Common Causes of Water Leaks and Waste
High water bills can be caused by a multitude of things, not just a hole in your pipe. The very first place a homeowner should look, after receiving a high water bill, is the bathroom(s). While a leaking toilet may not seem to discharge that much water, it does not take too long for the money to accumulate- maybe a gallon every five minutes, which would end up being 288 gallons of water in a day!
After checking the toilets, the next stop should be your water heater. If you have a tank type water heater, there is a Temperature and Pressure Relief Valve (T&P for short) that can discharge. If the T&P is causing your water bill to increase, chances are that the water pressure in your house is too high and a Pressure Reducing Valve (PRV for short) may be needed. There is a secondary issue of thermal expansion that may need to be addressed, depending on the last time your water heater was replaced (or, whether or not it was replaced by a reputable licensed plumber).
Thermal expansion is caused by the heating of water which leads to the spacing out of water molecules. This process will increase the water pressure inside your house (on the cold side, as well as, on the hot). If your water pressure is above 80PSI, either before or after thermal expansion, your water fixtures will be negatively affected. In fact, the plumbing code requires for PRVs to be installed if your pressure is above 80PSI and for a thermal expansion device to be installed if you have a backflow preventer and a tank type water heater. These provisions are for the sole purpose of protecting your investment in your home.
Lastly, if you have determined that your high water bill is not caused by old/faulty mechanisms in your toilet or on your water heater, it is best to call a licensed plumber or leak detecting professional.