Start at the meter
Turn off every fixture and appliance in the house, then look at the meter — most have a small triangle or dial that spins with any flow. If it's moving with everything off, water is leaving the system somewhere. If it isn't, the leak is intermittent (usually a toilet).
1. A running toilet
The number one cause. A worn flapper or a fill valve set too high lets water trickle into the bowl around the clock — hundreds of gallons a day, silently. Put a few drops of food coloring in the tank; if it shows up in the bowl without flushing, that's your leak. Cheap fix.
2. The water service line
If the meter spins with the house shut off at the main valve, the leak is between the meter and the house — underground. Look for a wet or unusually green spot in the yard. This is a repair or replacement of the service line.
3. Water heater or relief valve
A T&P relief valve that drips, or a tank weeping at a fitting, runs constantly into a drain where you never see it. Check the pan and the drain line from the relief valve.
4. Outdoor faucets and irrigation
A hose bib that didn't quite close, a cracked frost-proof faucet from last winter, or an irrigation zone valve stuck open. Walk the outside of the house.
5. Slab or crawl-space leaks
A warm spot on the floor, a musty crawl space, or a damp spot that never dries points to a supply line under the house. These need a plumber to locate; guessing means opening the wrong floor.
When to call
If the meter moves with everything off and you can't find it in ten minutes, call. Finding leaks is most of what we do, and the water you're paying for is probably costing more than the visit.
Written by the team at Good Help Plumbing, Nicholasville, KY. Questions about your own house? Call (859) 671-9213 — no service fee for local estimates.