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What to do if…
you find water collecting under a tiled floor and you suspect a leak beneath the tiles

Short answer

Stop the water supply to prevent spread: shut off your home’s main water valve (or the nearest fixture/appliance shutoff), keep the area safe, then call a plumber urgently.

Do not do these things

  • Don’t keep running water “to test it” or keep using the shower/tub/sink over the area.
  • Don’t turn on floor heat/underfloor heating, and don’t try to dry it by heating the floor from below.
  • Don’t pry up tiles or cut into the floor while the leak might still be active (and you may hit plumbing/heating/electrical lines).
  • Don’t use extension cords, space heaters, or plug-in dehumidifiers in/near standing water or where water might have reached outlets below/adjacent.
  • Don’t try to reach an electrical panel if you’d have to step in water or touch wet surfaces to get there.

What to do now

  1. Make a safer pause. Keep people and pets off the wet area. Treat loose tiles as a slip/trip hazard.
  2. Shut off the water.
    • If the source seems obvious and the area is dry/safe, close the nearest shutoff first (toilet/sink supply stops, appliance valve).
    • If the source isn’t obvious, shut off the home’s main water valve (often where the water line enters the home—basement, crawl space, garage, utility room, or an exterior wall; sometimes at the meter).
    • Open a faucet briefly to confirm the flow slows/stops.
  3. Reduce electrical risk (only if you can do it from a dry location).
    • If electrical circuits/equipment may be wet or near water, turn off power at the main breaker/service panel only if you can reach it without entering water.
    • If you would have to step into water or touch wet surfaces to access the panel, do not attempt it—call an electrician or your electric utility for help disconnecting power.
  4. Stop any likely appliance source. If an appliance line could be involved (dishwasher/washing machine/ice maker), shut the local valve if accessible and dry to reach.
  5. Contain and document (quickly).
    • Mop up surface water to reduce slipping and limit spread; place towels or a pan where water is emerging.
    • Take photos/video of grout seepage, tile lifting, wet baseboards/walls, and any nearby ceiling staining.
  6. Call for urgent help.
    • Contact a licensed plumber and say “water collecting under a tiled floor” and whether you have floor heat/underfloor heating.
    • If you’re in a condo/apartment, notify the property manager/HOA right away—there may be shared shutoffs and units below could be at risk.

What can wait

  • You don’t need to decide now about replacing tile, subfloor repair, or remediation vendors.
  • You don’t need to open the floor yourself “to locate the leak” before a plumber assesses it.
  • If you plan to involve insurance, that can usually wait until the water is off and help is on the way (your photos will help later).

Important reassurance

It’s frightening when water appears where you can’t see the pipework. Cutting off the water and avoiding electrical exposure are the most protective first moves, and they meaningfully limit how bad this can get.

Scope note

This is first-step stabilization only. The source could be supply plumbing, a drain/waste line, a shower pan, an appliance line, a slab leak, or a floor-heating system, and it often takes professional inspection to confirm.

Important note

This is general information, not professional plumbing or electrical advice. If you can’t safely shut off water or you think electricity is involved, prioritize safety and contact qualified professionals or emergency services as appropriate.

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