The situation
Illustrative example. Not a real job or customer.
An owner in a 1970s slab home receives a water bill far higher than the same period last year. Nobody new lives in the house, no pool was filled and nothing inside looks wet.
- The owner suspects the irrigation and checks for broken sprinkler heads, finding none.
- With all fixtures off and the irrigation valve closed, the meter's leak indicator still moves.
- A food coloring test shows every toilet flapper is sealing.
- Closing the house shutoff stops the indicator, so the leak is inside.
- Closing the water heater's cold inlet does not stop it, so the leak is likely on the cold side.
The owner has a confirmed cold-side leak inside the house with no visible sign, a common pattern when water drains into soil under the slab.
What each check ruled in or out
| Check | Result | What it told the owner |
|---|---|---|
| Irrigation valve closed | Meter still moving | Not the sprinklers |
| Toilet food coloring test | No color in any bowl | Not a toilet flapper |
| House shutoff closed | Meter stopped | Leak inside the house |
| Heater cold inlet closed | Meter still moving | Probably not the hot side |
How the leak was found
- Rule-outs reviewed.The plumber reviews the owner's notes and rechecks fixtures, the softener and the relief valve.
- Cold side isolated.A pressure test on the cold side confirms the owner's finding.
- Line traced.The cold line's route under the slab is traced from where it enters the house.
- Spot narrowed.Acoustic listening narrows the leak to an area under the laundry room floor.
- Repair chosen.Because the laundry floor is vinyl due for replacement anyway, the owner chooses a spot repair.
Why there was no warning on the floor
Cold water does not warm the floor, and when soil under a slab drains well, a leak can run for a long time without surfacing. The bill was the first visible sign. That is a good reason to compare bills with the same months last year rather than just with last month.
The owner also asked the City of Fullerton's water utility whether any leak-related billing adjustment might apply. Policies like that are set by the city, so checking with them directly was the right step.
Questions the owner asked along the way
- Could anything other than the cold line explain the meter movement?
- Why does the spot repair make sense here rather than a reroute?
- Who patches the concrete, and will the floor be ready for new vinyl?
- How will you test the repair before leaving?
Common questions
Is this a real customer story?
No. It is invented to illustrate a common sequence.
Can a slab leak really show nothing on the floor?
Yes. Cold-side leaks in particular may only show on the bill and the meter.
Does the city adjust bills for leaks?
That depends on the City of Fullerton's current policies. Check with the city's water utility.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.