Turn off every faucet and appliance, then look at the meter. If the little dial is still spinning, water is moving somewhere it shouldn't be.
Late at night, put your ear near the wet area. A faint hiss or trickle under solid floor is a strong sign of a line leaking below the slab.
If flooring is buckling or water is pooling, close your main shut-off valve to stop the flow while you wait for a plumber.
Pull up rugs and move furniture off the damp spot so moisture doesn't wick into more of your flooring.
Slab leaks happen when a water line running through or under the concrete foundation springs a leak. A lot of Monterey homes, especially newer builds in Marina, Seaside, and Del Rey Oaks, sit on slab foundations with the pipes cast right into them. Over time the copper corrodes, or a bad bend rubs against the concrete until it wears a hole. Warm floors mean it's the hot line. A damp patch that never dries, or a jump in your water usage, points to the cold side.
When our plumber arrives, they don't start jackhammering. They use camera inspection and electronic leak locating to pinpoint the exact spot before touching your floor. That saves your tile and your slab. From there you have options: spot repair at the leak, or rerouting that line so it no longer runs under the concrete. They'll walk you through what makes sense for your home.
Take this seriously. Water trapped under a slab has nowhere to go, so it works its way up through the floor and into your walls, and the damp coastal air here means it dries slowly. Left alone, it can crack tile, warp wood floors, and feed mold. If you're seeing a growing wet area or a water bill that doubled for no reason, call us. We roll out across the Peninsula and Salinas in about 45 minutes.
Describe what you're seeing to a real Monterey plumber: call (210) 555-0134 or send the form. Free, no obligation.