Homeowner guide
Signs of a Hidden Water Leak and How Plumbers Find It
A rising water bill, a meter that moves with every tap off, damp patches, musty smells or warm spots on the floor all point to a hidden leak. A plumber can usually find it without opening walls at random.
Hidden leaks are expensive because they run for weeks before anyone notices. The good news is that a simple meter test at home tells you within an hour whether you have one.
This guide lists the warning signs, the meter test, and what professional leak detection involves so you know what you are paying for.
Warning signs
- Water bill higher than the same season last year with no change in use
- Stains, bubbling paint or soft drywall on ceilings and walls
- A musty smell in a cabinet, closet or basement corner
- Warm spots on a floor over a concrete slab
- The sound of running water when everything is off
- A wet patch on the lawn in dry weather
The water meter test
Turn off every tap, appliance and the water softener. Note the meter reading or watch the small leak indicator dial. Wait one to two hours without using any water and check again. If the reading moved, water is escaping somewhere.
Then close the main shut-off and repeat. If the meter still moves, the leak is on the underground service line between the meter and the street. If it stops, the leak is inside the house.
How professional leak detection works
- Pressure testing isolated sections of pipe to narrow the location
- Acoustic listening equipment that hears water escaping under pressure
- Thermal imaging to find temperature changes behind walls and floors
- Moisture meters to map how far water has spread
- Camera inspection for drain and sewer leaks
- A small, targeted opening only once the leak is pinpointed
Questions to ask before booking
- Is the detection visit priced separately from the repair?
- Who opens and who patches the wall or floor?
- Will I get photos or a written note of where the leak was found?
Services covered in this guide
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