- Pooling in dry weather with a moving meter points to a water line leak.
- Pooling only after rain or watering is usually drainage or irrigation.
- Odor or slow drains suggest the sewer lateral, not the water line.
Three questions that solve most cases
- When does it appear? Only after rain or watering, or all the time?
- Where is it? Near a downspout, a sprinkler, the sewer cleanout, or on the line between the water meter and the house?
- Does the meter move with everything off?
The six usual causes
1. Poor drainage after rain
Low spots, compacted soil and clay that drains slowly can all hold water after a storm. Clue: it appears after rain and fades over the following days. The meter is still.
2. Downspouts and roof runoff
A downspout discharging onto a flat lawn or near the foundation can create a soggy zone. Clue: it's next to a downspout and tracks the weather.
3. Irrigation leaks and overspray
A cracked lateral, a broken head or a weeping valve is one of the most common causes of year-round wet spots. Clue: it's near a valve box or head and gets worse after the system runs. The meter stops when the irrigation supply is closed.
4. A leaking water service line
The pressurized pipe from your meter to the house leaks continuously, so the wet area persists regardless of weather or watering schedule. Clue: it's roughly between the meter and the house, it doesn't dry out, and the meter keeps moving with the house and irrigation both shut off. See signs of an underground water line leak.
5. A sewer lateral problem
A cracked or blocked sewer lateral can surface wastewater. Clue: odor, slow or gurgling drains, and a location along the sewer route rather than the water line. That's a different repair entirely.
6. Natural groundwater or a spring
On some lots, especially at the base of a slope, groundwater seeps to the surface seasonally. Clue: it follows wet seasons and the meter is still.
Match the pattern
| Pattern | Most likely cause |
|---|---|
| After rain only, dries in days | Drainage or runoff |
| After sprinklers run | Irrigation leak or overspray |
| Constant, between meter and house, meter moving | Water service line leak |
| Smell, slow drains | Sewer lateral |
| Seasonal, at the base of a slope | Groundwater |
The five-minute test
Shut off all water use, close the building shut-off and the irrigation supply, then watch the meter. If it still moves, your water service line is leaking. The City of San Luis Obispo's leak guidance covers the first part of this; our meter guide covers the rest.
If it's the water line, underground water line repair starts with pinpointing the leak so only a small area is dug. The leak repair page walks through the process, and our homepage explains water line repair in San Luis Obispo, including who owns which section of pipe.