Most calls about a high bill sound the same. Winter looked normal, then the summer number doubled, and nothing obvious changed in the yard. In an inland climate the irrigation system is doing most of the work from May through September, so that is where the money goes when a bill climbs. Three causes cover the large majority of cases, and you can rule each one in or out yourself in about twenty minutes.
Start with the controller
A schedule set in spring runs the same minutes in September, when the days are shorter and the plants need less. That alone can put a system 30 to 40 percent over what the landscape actually uses. Open the controller and read what it is set to: how many start times, how many minutes per zone, which days. A common find is a second start time somebody added during a heat wave and never removed, so every zone runs twice a night.
If the controller is a basic timer, this is the season it costs you. A weather-based controller adjusts run times to the local evapotranspiration rate on its own, and on most properties it is the single biggest water saver available. California's water-efficiency ordinance requires one on qualifying projects for exactly this reason.
Then check the valves
Walk the yard while a zone is running and look at the zones that are supposed to be off. A valve that will not fully close weeps into its zone 24 hours a day. You will not see it running like a normal cycle — you will see a patch that is always wet, or a low spot that never dries, or a slow trickle at the lowest sprinkler head on that line. A weeping valve can waste more water than a broken pipe because it never stops and nobody notices.
Then look for a leak
With every zone off and no water running in the house, go to the meter and watch the small dial or the leak indicator. It should not move at all. If it creeps, water is moving somewhere — usually a cracked lateral line, a fitting that let go, or a drip line that a shovel or a rodent opened up. Mainline leaks between the meter and the valves are the worst of these, because that section is under pressure all the time.
If the controller looks sane, the valves all close, and the meter holds still with everything off, the system is probably fine and the bill increase is just seasonal demand. If any of the three checks fails, that is your answer, and it is worth fixing before the next billing cycle rather than after.
