When a water heater is installed outside the basement, what must it be placed on?

When installing a water heater outside of a basement, a safety pan must be used to ensure proper drainage and to protect against potential leaks or spills. A safety pan is specifically designed to catch any water that may escape from the unit due to overflows, leaks, or condensation, preventing water damage to the surrounding area.

This safety requirement is particularly important for installations where the water heater is positioned in locations that might not have direct drainage, as is the case when it is located outside a basement. The safety pan typically includes a drain line connected to the home's drainage system, ensuring that any captured water is safely directed away from the heater and structure.

The other options might not provide the same level of protection against water damage. A concrete slab, while sturdy, does not offer a mechanism for catching leaks. A wooden base could be susceptible to rot and decay from water exposure. A metal platform also lacks drainage capabilities, which can lead to issues if leaks occur. Thus, the use of a safety pan is the most effective choice for ensuring both safety and convenience in managing potential water issues around an outdoor water heater installation.