Last reviewed and updated: 2026-09-24
An irrigation leak sits on your side of the meter but runs underground on an automatic schedule, usually overnight. A cracked lateral, a sheared head or a valve that fails to close fully can waste thousands of gallons before any symptom appears. Isolate the irrigation supply and watch the meter: if the meter stops when irrigation is closed but runs when it is open, the system is the source.
Irrigation runs underground, overnight, on a timer, which makes it the most easily missed cause of a high water bill in Cobb County. It tees off the service line, so the two are separated at the meter. Across a larger site the same problem is found with a commercial water loss audit.
Signs of an irrigation leak
- The meter moves with the house main closed but the irrigation supply open: the definitive test
- One zone that is always wetter, or an area that stays soggy between cycles
- Heads that weep or trickle when the system is supposed to be off
- Poor pressure or weak spray in one zone while others are fine
- Erosion, sinking or a washed-out channel along a buried lateral
- A bill that rises in spring when the controller comes back on for the season
Isolating the system
- Turn the controller off entirely. Not to a rain delay, fully off, so no zone can fire during testing.
- Close the house main, leave the irrigation supply open. Watch the meter. Movement now means the leak is on the irrigation line.
- Close the irrigation supply too. If the meter stops, the irrigation system is confirmed as the source.
- Test zone by zone. Run each zone manually and watch pressure, spray pattern and the ground surface. A zone that will not build pressure has a break.
- Check each valve. A valve that does not seat fully lets water through continuously into that zone, even with the controller off.
- Trace and listen. A pressurized lateral leak can be located acoustically along the buried run, so only the failure point is dug.
Common failure points
- A valve that will not seat: debris or a worn diaphragm leaves it partly open, running water constantly.
- Cracked laterals from ground movement in Georgia clay, freeze damage, or a shovel.
- Sheared or damaged heads from mowers, vehicles or foot traffic.
- Failed backflow preventer at the connection point.
- Freeze damage in exposed above-ground components after a hard Marietta winter.
Seasonal pattern worth noticing. If your bill jumps every spring when the controller comes back on and settles when it is shut down for winter, the irrigation system is the obvious first suspect.
Frequently asked questions
How do I know if my sprinkler system is leaking?
Turn the controller fully off. Close the main house shut-off valve but leave the irrigation supply open, then watch the meter. If it moves, the leak is on the irrigation line. Close the irrigation supply too: if the meter then stops, the system is confirmed as the source.
Why does an irrigation leak waste so much water?
Because it is underground, on an automatic schedule, usually overnight, and produces no indoor symptoms at all. A cracked lateral or a valve that fails to close fully runs continuously for weeks before anything visible appears at the surface.
What are the most common irrigation leak points?
A valve that will not seat fully because of debris or a worn diaphragm, cracked laterals from ground movement or digging damage, sheared heads from mowers and vehicles, a failed backflow preventer, and freeze damage to exposed components.
My water bill goes up every spring. Is that the sprinklers?
Very likely. If the rise coincides with the controller coming back on for the season and settles again when the system is shut down for winter, the irrigation system is the first place to look,either an actual leak or a schedule running longer than you think.
Can an underground irrigation leak be found without digging up the lawn?
Usually. Zone-by-zone testing narrows it to one lateral, and a pressurized lateral leak can then be located acoustically along the buried run, so only the failure point is excavated.
Does an irrigation leak qualify for a Cobb County water bill credit?
Generally yes, as a plumbing failure, provided you document the repair. Note which zone failed and what was replaced: a parts receipt can serve as the proof Cobb County requires.