What is the recommended pipe size for the main fuel supply line to a water heater or furnace?

The recommended pipe size for the main fuel supply line to a water heater or furnace is typically 3/4 inch. This size is commonly accepted for ensuring adequate gas flow to standard residential water heaters and furnaces. A 3/4-inch pipe can effectively transport natural gas or propane to these appliances while minimizing pressure loss that can occur with smaller pipes.

Using a pipe that is too small may result in insufficient gas supply, which can lead to poor performance of the heating equipment, increased operating costs, and potentially unsafe conditions. Conversely, larger pipe sizes, while they can carry more gas, may not be necessary and could lead to unnecessary expenses in terms of material and installation.

Therefore, 3/4 inch is considered a practical and efficient choice for most home heating applications, balancing the need for adequate fuel supply while being cost-effective.