What size gas line for 400000 btu pool heater?

For a 400,000 BTU pool heater, a minimum gas line size of 1 inch is generally recommended for natural gas. If using propane, a 1 1/4 inch gas line may be required to ensure adequate gas flow. Always consult local codes and a professional to determine the appropriate line size based on your specific installation conditions. Proper sizing is crucial for safety and efficiency.