A warm spot that is obvious at 7 a.m. after showers may be gone by afternoon. A hiss heard at midnight may be drowned out during the day. Logging what you notice, when you notice it, helps separate a real under-slab leak from coincidences like sunlight on tile or a sprinkler cycle.
Keep the log for a few days to a week if the leak is slow and nothing is surfacing indoors. If water is coming up through the floor, skip the log, close the main and get help.
Daily log
| Date and time | Warm spot (where, how warm) | Damp or smell (where) | Sounds | Meter indicator | Water just used? |
|---|---|---|---|---|---|
| ______ | ______ | ______ | ______ | moving / still | ______ |
| ______ | ______ | ______ | ______ | moving / still | ______ |
| ______ | ______ | ______ | ______ | moving / still | ______ |
| ______ | ______ | ______ | ______ | moving / still | ______ |
| ______ | ______ | ______ | ______ | moving / still | ______ |
How to check each time
- Floor.Walk the suspect area barefoot or with the back of your hand. Mark the warmest point with painter's tape and write the time on the tape.
- Edges.Look at baseboards, carpet edges and grout lines near the warm area. Mark the edge of any dampness.
- Listen.With nothing running, stand quietly in the room and near the water heater. Note any hiss or trickle.
- Meter.If you can get to the meter, note whether the leak indicator moves with everything off.
- Context.Write down what water was used in the last hour: showers, laundry, dishwasher, irrigation.
Monthly bill comparison
| Billing period | This year usage | Same period last year | Anything different at home? |
|---|---|---|---|
| ______ | ______ | ______ | ______ |
| ______ | ______ | ______ | ______ |
| ______ | ______ | ______ | ______ |
Questions your log can answer
- Is the warm area tied to hot water use?
- Does the meter move even when nothing is scheduled to run?
- Is dampness spreading, stable or drying out?
- Did the signs start after a specific event, such as a new appliance or a pressure change?
Common questions
How long should I keep the log?
A few days is often enough to see a pattern. If water is surfacing indoors, do not wait; close the main and get help.
Can a thermometer help?
An inexpensive infrared thermometer can show temperature differences across a floor, which makes your notes more precise.
What should I bring to the plumber?
The log, your meter worksheet, recent bills and photos of the marked areas.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.