Last reviewed and updated: 2026-09-24
A patch of lawn that stays soggy or grows noticeably greener in dry weather is usually a buried water service line leak, an irrigation lateral leak, or a sewer lateral leak. Clean water from a supply line produces a soft, soggy patch with no smell. A sewer leak produces lush growth and usually an odor. The meter test distinguishes them: a turning meter with the house main closed confirms a supply-side leak.
A patch that stays wet is nearly always the buried service line or an irrigation lateral. Water travels before it surfaces, so the wet spot is rarely above the break.
Which is it?
| Clue | Supply line | Irrigation | Sewer lateral |
|---|---|---|---|
| Smell | None | None | Often present |
| Grass | Soggy, may drown out | Soggy in one zone | Unusually lush and dark green |
| Meter with house main closed | Still turning | Stops if irrigation supply closed | No movement |
| Timing | Constant | Worse after a watering cycle | Worse after heavy indoor water use |
| Water bill | Rising | Rising | Normal |
| Ground | Soft, sometimes sinking | Soft along a lateral route | Soft, sometimes sunken |
Confirm it
- Run the meter test. Everything off. Movement means a supply-side leak.
- Close the main house valve. If the meter still turns, the leak is between the meter and the house, the buried service line.
- Isolate irrigation. Turn the controller fully off and close the irrigation supply. If the meter stops, it is the sprinkler system.
- Smell the area. A sewer odor points to the lateral rather than a supply line.
- Note where it sits. A wet patch roughly along the line from the meter to the house points to the service line; one running toward the street from the house points to the sewer lateral.
- Do not dig to look. Water travels underground before it surfaces, the wet patch is frequently not above the break.
The wet spot is not the leak. Depending on soil, depth and slope, water can travel a considerable distance before surfacing. Digging where the ground is wet is how people end up with several holes and an unfound leak. Tracing and correlation put the hole in the right place.
Frequently asked questions
Why is one patch of my lawn always wet with no rain?
Something underground is watering it, most often a buried water service line leak, an irrigation lateral leak, or a sewer lateral leak. The meter test tells you whether it is coming from your pressurized supply.
How do I tell a water leak from a sewer leak in the yard?
Smell and the meter. A supply line leak produces clean water, no odor, and a meter that keeps turning with everything off. A sewer leak often produces an odor and unusually lush dark green growth, and does not affect the water meter at all.
Why is the grass greener over a leak?
Constant moisture, and in the case of a sewer leak, nutrients. A patch that is noticeably greener and growing faster than the lawn around it in dry weather is a classic sign of a sewer lateral leak.
Should I dig where the ground is wet?
No. Water travels underground along the path of least resistance before surfacing, so the wet patch is frequently not above the break. Line tracing and leak correlation locate the actual failure point so only one hole is needed.
Who pays for a leak in the yard?
You do, if it is on the house side of the meter, which includes the buried service line, the irrigation system and the sewer lateral. The utility is responsible for the main and the meter itself.