Look for the cold water shutoff valve on top of the tank or the line feeding it. Turn it clockwise until it stops. This stops fresh water from filling the leaking tank.
If you have an electric heater, flip the breaker to OFF. If it's gas, find the control dial on the side and switch it to OFF. Do not light it again until a plumber checks it.
Hot water under pressure makes a leak worse. Wait before you touch anything. Then look underneath with a flashlight to see where the water is coming from.
A water heater can dump fifty gallons or more across your floor if the tank ruptures completely. A plumber can replace it the same day and get your hot water back.
A leak from the bottom of the tank means the interior protective layer has failed. Most water heaters last twelve to fifteen years. In Santa Cruz, where our water is mineral-rich from the aquifer, that rust-resistant lining corrodes faster. Once it goes, the metal underneath starts to weep, and you can't patch it.
The plumber will check whether the leak is coming from the tank itself or from a fitting, valve, or connection point near the base. Leaks from fittings sometimes get fixed without replacing the whole heater. But if water is actually coming through the tank wall, replacement is the only real answer. A plumber can tell in seconds.
Don't wait for this one to get worse. A small leak from the bottom will become a big one. When it does, you lose all your hot water, and water spills across your floor and into crawl spaces or basements. If you have a slab foundation, water can migrate into the soil and cause damage you won't see until later. A same-day or next-day replacement stops that.
Describe what you're seeing to a real Santa Cruz plumber: call (831) 555-0115 or send the form. Free, no obligation.