How can you tell whether a pool heater is to burn propane or natural gas?

To determine whether a pool heater uses propane or natural gas, check the manufacturer's specifications or the label on the heater itself, which usually indicates the type of gas it is designed for. Additionally, the connection type can provide clues; propane typically requires a larger tank and a different regulator compared to natural gas. If there's uncertainty, consulting a professional or the owner's manual can clarify the heater's requirements.