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 suited for delivering natural gas or propane to most residential appliances, balancing the need for adequate gas flow with efficiency and safety requirements.

Using a 3/4 inch pipe can effectively handle the gas demand of most standard water heaters and furnaces, ensuring that they operate efficiently and maintain proper combustion. In some cases, larger pipe sizes like 1 inch might be applicable based on specific equipment requirements or unique installation scenarios, but for typical residential setups, 3/4 inch is generally the most recommended and widely accepted size.

Selecting a larger pipe, such as 1.5 or 2 inches, can lead to unnecessary costs and complications without providing a proportional benefit for most residential applications. It is important to assess the specific needs of the appliance and the layout of the gas supply system to determine the most appropriate size.