Stop the source safely
If the leak is active, shut off the water supply when you know how to do so safely. Because water heaters involve utilities, use appropriate caution around electrical or gas connections and contact the relevant trade professional when needed.
Check nearby rooms and lower levels
Water can move along walls and floors or pass through openings into adjacent spaces. A utility room or garage leak may affect finished areas that are not immediately visible.
Drying matters after the repair
Replacing or repairing the water heater does not dry the materials around it. Wet flooring, drywall, baseboards or cabinets may still need restoration attention.