Locate and watch the low flow indicator on the meter.
First, make sure no water is being used in the house (washing machine, dishwasher, ice maker, toilet flushing, etc.). Go out to your meter and watch the low flow indicator. The low flow indicator is a small diamond or triangle located on the meter face. If this indicator is turning, even slightly, then there is water moving through the meter. This is a good indication of a leak.
Try to determine location of leak by isolating your home.
Locate the main water shutoff valve to your home. This valve may be located in your mechanical room, water heater closet, or possibly in the crawlspace or basement. By turning this valve off, you are shutting off all water to the house.
Recheck the low flow indicator.
If it has stopped turning, then the leak is most likely inside your home and you can begin to look for possible leaks inside your home. If the indicator is still turning, then the leak is between the meter and the house, most likely on the underground piping. Remember to turn the main valve back on when finished.
MOST COMMON LEAKS
The most common leak inside the home is the flapper in a toilet that is not sealing properly. You may hear the toilet refill itself even though it has not been used, or sometimes you can actually see the water trickling inside the bowl when the toilet is not in use. A good way to check for this is a dye test. Lift the lid off the tank of your toilet and put a few drops of food coloring into the water. After 15-30 minutes, if the water in the bowl turns the same color as the dye, then you have a leaking flapper. A toilet flapper is inexpensive, is easy to replace and can be purchased at most hardware stores. This type of leak could cost you on your monthly bill between $20 and $30 dollars.
Toilet float valve.
As a toilet refills itself after each use, the water will lift a float in the tank that shuts off the water once the correct level is reached. Over time, this valve may allow the water to run continuously into the tank and down the overflow tube. To see if this is happening, lift the lid off the tank of your toilet and flush. After the water has risen to a certain level, the float should stop the water. If the water continues to flow, or if water is going down the overflow tube, then the float will need to be adjusted or replaced. This type of leak could cost in excess of $40 to $70 on your monthly bill.
Outside faucets or hoses
Check to see that your outside faucets are shutting off completely. If they drip, they may need new seals or need to be replaced. Other symptoms of a leak on your outside faucet are low water pressure or a strange hissing noise when you turn it on.
Washing machine water lines
Check behind the clothes washer for any moisture. The connections and the supply lines from the wall to the machine should be dry to the touch. These are often overlooked and can leak over time, causing high water bills and water damage.
Most water softeners have a backwash mode to clean the system periodically. When a softener system malfunctions, it can continually run water through the machine and into the drain system. If you feel this may be the case, please call your water softener company or plumber to have the system checked.
Refrigerator icemaker lines.
If the refrigerator is equipped with an icemaker, there will be a small water line behind the refrigerator supplying the water. Look for moisture behind the appliance. Look at the connections and the hose for leaks.
Leaks in the crawlspace.
Most homeowners never check under their home, but a leaking of broken pipe in the crawlspace may never be notices if the water is being absorbed in the ground. Use a flashlight and look for standing water, puddles, or muddy spots. Listen for water running, dripping sounds, or hissing.
Irrigation system leaks.
Leaks are common on in-ground irrigation systems and may be difficult to locate. Sprinkler heads are easily damaged from lawn mowing equipment and should be checked periodically. Regular maintenance should be completed by your irrigation contractor and should be contacted if you suspect a leak.