- Dry-weather dampness is the most telling surface sign.
- Water can surface several feet from the actual leak.
- Confirm with the meter before assuming it's the water line.
Here's what makes buried leaks tricky: the pipe is pressurized, the soil is porous, and water follows the path of least resistance. It often travels along the loose backfill of the original trench before it surfaces, if it surfaces at all. So the signs are often indirect.
The surface signs
Soggy or spongy ground
Ground that squelches underfoot, or stays dark and damp when everything around it has dried, is the most common sign. It's most telling in the dry months, when rain and dew can't explain it.
Puddles and pooling
Water collecting in a low spot, seeping out at the edge of a walkway, or trickling down a slope with no obvious source. See why water pools in a yard for the other possible causes.
A greener, faster-growing strip
During a dry spell, grass or weeds growing noticeably lusher along a line across the yard can trace the route of a leaking pipe.
Sinkholes and settling
Escaping water washes fine soil away, leaving voids. A new depression in the lawn, a paver that has dropped or a slab that has tilted can all be signs. Treat any hollow-feeling area with caution.
The signs you can't see in the yard
- Unexplained usage: a bill that has jumped with no change in habits, or a smart-meter leak notification. In San Luis Obispo, the City's AMI customer portal lets account holders set leak thresholds.
- A moving meter: the low-flow indicator turns with everything off.
- Low or falling pressure: larger leaks divert enough water to notice at the tap.
- Sounds: a hiss at the meter box or the hose bib nearest the street.
Is it the water line or something else?
| Possible source | Clue |
|---|---|
| Water service line | Wet area between meter and house; meter moves with house and irrigation shut off |
| Irrigation leak | Wet area near a sprinkler valve or head; meter stops when irrigation is isolated |
| Sewer lateral | Odor, slow drains, wet area along the sewer route (not a pressure leak) |
| Drainage/runoff | Appears after rain or irrigation and dries in between |
Confirm before you dig
The quickest confirmation is the meter test with the building shut-off and irrigation both closed. Our meter check guide walks through it. If the meter still moves, the service line is leaking.
Why you shouldn't wait
A buried leak runs 24 hours a day. Beyond the water cost, saturated soil can undermine walkways, driveways and, near the house, foundations. In clay-rich soils that swell when wet, that extra moisture can add movement too.
Once a leak is confirmed, underground water line repair starts with pinpointing it so the dig is small; our leak repair page explains the process. For the full local picture, see our overview of water line repair in San Luis Obispo, CA.