The situation
Illustrative example. Not a real job or customer.
In a single-story, slab-on-grade Fullerton tract home from the 1960s, the flooring just outside the hall bathroom's tub-shower feels damp and the baseboard is darkening. The family assumes the tub is leaking and plans to regrout.
- Before regrouting, they turn off every fixture and watch the water meter. It keeps moving slowly.
- They close the valve stops behind the shower trim. The meter still moves.
- They check toilets for running water and find none.
- The damp area stays the same whether or not the shower or tub is used.
The evidence points away from the shower and toward a supply line leak, possibly in or under the slab.
Shower leak versus supply leak
Shower or tub leak
- Damp changes with shower or bath use
- Meter is still with everything off
- Fixed with seals, gaskets, grout or a valve
Supply line leak
- Damp is constant regardless of use
- Meter moves with everything off
- Needs leak detection to locate before opening anything
What a sensible next step looks like
- Shut off when not needed.Close the main overnight to limit water under the floor until the leak is found.
- Leak detection.A plumber uses listening equipment, pressure testing or thermal imaging to locate the line before cutting floors.
- Choose a repair.Options can include a spot repair through the slab or rerouting the line; the plumber explains which fits.
- Dry the floor.Once the leak is fixed, flooring and baseboard are dried and repaired.
The lesson
Damp next to a shower naturally makes people suspect the shower. In older Fullerton slab homes with copper or galvanized supply lines running under the floor, a constant leak nearby is also possible.
Regrouting would have spent effort on the wrong problem while the leak kept running. The meter test took fifteen minutes and changed the whole plan.
Common questions
Is this a real case?
No. It is an invented example.
Why close the valve stops in the test?
If the meter had stopped, the leak would have been at the shower valve. It kept moving, so the leak was elsewhere.
Can I ask you about a leak like this?
You can send us the details, but this is a preview site: the phone number shown is a temporary placeholder and the request form is not connected yet, so a submission is not sent anywhere.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.