How To Find a Hidden Water Leak

How to do a water meter leak test

1. Turn off every faucet, shower, appliance, ice maker, water softener and irrigation system. Make sure nobody uses water during the test.
2. Find your water meter, usually in a box near the street or sidewalk. Lift the lid carefully.
3. Look at the small leak indicator (often a triangle or star). If it's spinning with everything off, water is flowing somewhere.
4. Write down the full meter reading, wait 30–60 minutes (or longer), and read it again.
5. Enter both readings in the calculator above to see your leak rate.

Narrowing down where it is

• Toilets first. Add a few drops of food coloring to the tank, wait 15 minutes without flushing. Color in the bowl means a leaking flapper, the most common silent leak.
• Close the house shutoff. If the meter stops, the leak is inside the house. If it keeps moving, the leak is in the yard line between the meter and the house, or in irrigation.
• Check the water heater. Look for water in the pan or around the base, and listen for constant refilling.
• Look for heat. Warm spots on floors point to a hot-water slab leak.
• Listen. At night, a hissing or rushing sound in walls or under floors is a clue.

Signs of a leak inside walls or ceilings

• Stains, bubbling paint or soft spots on drywall
• Warped or stained baseboards
• Musty smell in one area that doesn't go away
• Mold on walls or the back of cabinets
• Loose tile or cupped flooring near a wall with plumbing

Once you find it

Fix the source, then deal with the water it has already released. A leak that has been running for weeks has usually soaked framing, insulation or flooring beyond what's visible. Moisture mapping shows how far it went, and structural drying dries it before mold takes hold. Long-term leaks may not be covered by insurance, so act as soon as you find one.