Many of us have been there. You may either receive an abnormally HIGH water bill or a notice from your water company about a suspected leak. The main reason a water supplier may alert you is because your measured numbers were abnormally high (per the meter) and/or the timing/duration of use is abnormal - all of which means they are suspect a leak is on your side of the meter. You may want to simply call a plumber or irrigation service now which is perfectly fine, but if you're the investigative type, here are some tips on how to proceed with possibly discovering the leak source prior to calling a service company. Fixing it may still require calling someone, but this may help determine who to call. Your situation may vary if you have multiple water meters (1 for irrigation and 1 for your home, or one for a pool set-up) but this will apply to most set-ups. NOTE: Traditionally, if a leak is on the supply/street side of a meter, it's the responsibility of the water supply company/municipality to resolve. If a leak is on the property owner's side of the meter, it's their responsibility to resolve. It should also be noted that some water suppliers will work with property owners on adjustments to a high bill if an affidavit is supplied stating a leak was discovered and repaired.
Let's take a few steps to see if you can discover the source of your leak. Keep in mind that a leak will only "run" when it has water supplied to it, so if a valve of any sort turns water on and off to the leak location, it could only leak when the valve is on, so if anything is on timers or inside appliances the leak may vary with timing making it more difficult to find. We'll attempt to find it regardless.
Now, let's see if we can separate your home from your irrigation system (this is assuming you're running everything through 1 water meter).
If the meter numbers kept moving after you shut off the home's valve and you've concluded that the leak is OUTSIDE of your home, then here are some things to consider for leak sources:
If the meter's numbers stopped moving when you shut off the home and you've concluded that the leak is INSIDE of your home, then here are some things to consider.
Some of the home leaks can be fixed by an ambitious DYIer. Toilet tank seals and valves are easily resolved with a trip to the home improvement store. Some seals are even available in a higher grade than what originally ships, so that may be something to investigate to provide longevity.
Multiple Water Meters
This is going to be more the exception than the rule. If you by chance have multiple water meters, then a similar approach will be used for each meter to isolate the area of the leak. You' want to isolate each area while checking the meter's gauge for movement. Why multiple meters? In some areas, property owners are billed for water in and sewage out. Sewage out is partially calculated on the water in. They figure if water came into your home, then it went back out for processing too, so they charge accordingly and that may be about 50% of your bill. As we all know, not all water goes back out the sewer line. We water lawns, wash cars, kids may play in the sprinklers, but the water company cannot account for all of that for every single property owner, so their system simply assumes water in is sewer out, but they often offer an alternative. That is to install a second water meter for purposes where the water is NOT going back out the sewer line such as in irrigation system. When you run an irrigation system through a second dedicated meter, you are not billed for those gallons as sewer out. It's not free though. You'll pay a substantial connection fee (often a few thousand dollars) for the ability to connect. Once done though, and if you're at that property for the long haul, the expense can wash out and result in a long term savings.
No mater which set-up you have, isolation of areas is the key to finding a leak's location. By properly utilizing valves, you can narrow the location of your leak and better know which service person to contact for a repair. As mentioned, be sure to ask your water supplier about options for adjustments to high water bills. It should also be noted that if a home is new, the irrigation was set up by the installer, and a homeowner is new to using irrigation that homeowner may be initially surprised at their water bill... even if it is actually correct (leading them to believe they have a leak). It's astonishing how much a properly watered lawn consumes, so irrigation systems are often dialed back to stay on budget. Having a point of reference (like previous years' use) is a great way to determine if consumption is off the norm and if you possibly have a leak... which is what the water company is doing if they send you a notice.
All the luck with resolving any water issues.