A wet area that never dries is usually an irrigation leak, a valve seeping into a lateral, or water surfacing from a break further uphill. It can also have nothing to do with irrigation at all — a low point collecting runoff on clay soil behaves the same way. The meter test settles it: if the meter moves with all water use stopped, you are losing treated water and it needs finding.
Irrigation or drainage? The test that separates them
Stop all indoor water use, switch the controller off, and watch the water meter for fifteen minutes. If the meter turns, water is being supplied continuously and you have a leak on the pressurised side — mainline or a valve not sealing.
If the meter is completely still and the ground is still soggy days after the last rain, then nothing is being supplied and the water is either already in the soil or arriving as runoff. That is a drainage problem, not an irrigation problem, and no irrigation repair will fix it.
The third case is a lateral leak, which shows as a meter that stays still with the controller off but an area that gets noticeably worse each time one specific zone runs. Running each zone for a few minutes and watching is how that gets confirmed.
Why the soggy patch is often not above the break
Piedmont clay has low permeability, so water leaving a broken pipe does not soak straight down. It follows the loose backfilled soil of the original pipe trench, which is the easiest path available, and it runs downhill with the grade. It surfaces wherever the grade flattens, where the trench meets a soil change, or against something solid like a footing or a driveway edge.
The practical result is that the visible wet spot is frequently downhill of the actual break, sometimes by a good distance. That is why the diagnosis starts with the meter and the zone-by-zone test rather than with a shovel at the wet point.
The specific irrigation causes
| Cause | Telltale |
|---|---|
| Mainline leak | Meter turns with the controller off; often reduced pressure everywhere |
| Valve not sealing | Meter turns; water trickles from heads on one zone continuously |
| Lateral line break | Meter still with system off; area worsens when one zone runs; that zone performs poorly |
| Cracked or seeping valve box fitting | Valve box holds water constantly; ground around the box stays wet |
| Low-head drainage | Water weeps from the lowest heads after a cycle, then stops. Not a fault. |
| Misaligned or stuck head | One area receives every cycle twice over while the rest is normal |
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When it is genuinely a drainage issue
Clay soil, a low point in the grade, a downspout discharging nearby, or compacted ground under a former construction access route will all hold water for days after rain with no irrigation involvement whatsoever. Sloped North Georgia lots produce this reliably at the bottom of the grade, where everything above drains to.
The other version worth naming is overwatering. A zone at the bottom of a slope receives its own irrigation plus runoff from everything uphill of it, and if it is on the same run time as the zones above it, it will stay saturated all season. That is a scheduling and zoning correction — shorter cycles with soak periods, and grouping heads by elevation — not a repair.
Why not to leave it
- A continuous leak on the pressurised side runs all day, every day, and generally outruns the cost of the repair inside a billing cycle or two.
- Saturated ground beside a driveway, walkway, patio or retaining wall undermines the base material and leads to settling and cracking.
- Persistently saturated soil kills turf and shallow-rooted plantings as effectively as drought does.
- A slow leak enlarges. Water moving through soil carries fines away, the void grows, and pipe left unsupported eventually fails more comprehensively.
Related answers
- How Do You Find an Underground Sprinkler Leak?An underground irrigation leak is located by measuring, not by looking. A technician isolates the system at the irrigation shutoff valve and watches…
- What Is the Difference Between a Mainline and a Lateral Line Leak?A mainline leak is on the pipe upstream of the zone valves, which is pressurised around the clock, so it wastes water continuously and is the more…
- Why Is My Sprinkler System Leaking When It Is Turned Off?Water moving while the system is off means something on the pressurised side is failing, because the mainline holds pressure around the clock even…
- Why Is My Valve Box Full of Water?A valve box full of water means either something in the box is leaking or water is getting in from outside and cannot drain. A seeping valve or a…
Services that fix this
Irrigation Leak Repair
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Irrigation Medics repairs irrigation systems across Hall County and the Lake Lanier communities, the Gwinnett corridor through Duluth, Suwanee and Buford, and North Fulton and Forsyth — Johns Creek, Alpharetta, Milton, Roswell and Cumming. Same rates throughout. See the service area.