Find where water starts
Dry the area and watch the connections, relief-valve pipe, drain valve, and tank seam. Water from a fitting may be repairable; water through the tank body usually indicates tank failure.
Shut down only what you can identify
Close the cold-water supply above the heater if it is clearly labeled. For an electric heater, turn off the dedicated breaker. If you smell gas, leave the area and call the gas utility or emergency services.
Do not wait on a tank leak
A small leak can become floor, wall, or ceiling damage. Take photos, move stored items, and ask whether repair, replacement, pan drainage, expansion control, and code updates need to be considered.
Questions to ask before replacement
Ask about capacity, recovery, fuel type, location, code requirements, expansion control, pan drainage, and the condition of the shutoff. These details affect the installed project and future reliability.
After the work is complete
Confirm that the new unit is level, the valves are labeled, the relief line is installed correctly, and the area is dry. Keep the installation information and warranty where it can be found later.