Find the cold water valve on top of the heater and turn it clockwise until it stops. This stops more water from feeding the tank.
For an electric unit, flip the breaker. For gas, turn the dial on the front to the "off" position. This keeps the burner or elements from running dry.
Dry the floor, then watch where the water comes back. Drips from the drain valve or a fitting can be fixed. Water seeping from the base of the tank means the tank is done.
Move boxes, laundry, and anything that soaks up water away from the heater so you can see the leak and protect your stuff.
Most tank heaters last a good while, but the steel tank slowly corrodes from the inside. Once it rusts through, water weeps out the bottom and no patch will hold. That's the most common reason for a puddle under the unit. The fix is a new heater, not a repair.
Not every bottom leak is fatal, though. A drippy drain valve, a loose cold or hot water fitting, or a leaking temperature and pressure relief line can look the same from across the garage. A plumber checks each of these first before recommending a replacement. In a lot of Castroville and Prunedale homes the heater sits in the garage or a closet, so a slow leak can run for weeks before anyone notices the damp drywall.
The hard water common around the Salinas Valley speeds up sediment buildup at the bottom of the tank. That sediment traps heat, stresses the steel, and shortens the tank's life. If your heater rumbles or pops when it runs, that's the sediment, and it's a sign the unit is aging.
Treat it as urgent if water is spreading fast, if you smell gas, or if the heater is near an electrical panel or finished living space. A steady flow can flood a garage in Marina or Salinas quickly. We keep a plumber close, usually about 45 minutes out, to shut things down and get you a working replacement.
Describe what you're seeing to a real Castroville plumber: call (210) 555-0134 or send the form. Free, no obligation.