What is the minimum size of a supply line for fuel oil systems in terms of inside diameter nominal pipe?

The minimum size of a supply line for fuel oil systems is determined by the need to ensure adequate flow without causing excessive pressure loss or other system issues. A nominal pipe size of 3/8 inch in inside diameter is specified as the minimum because it strikes a balance between the ability to transport fuel efficiently and the risk of vapor lock or insufficient flow.

Larger diameters could be more efficient, but they are typically unnecessary for most residential and light commercial fuel oil applications, which often require just a steady and reliable supply that's easily managed by a 3/8 inch line. Using a supply line that is too small, such as 1/4 inch, might lead to constraints in flow, potentially causing operational issues. Sizes like 1/2 inch or 1 inch may be suitable for higher demands or commercial applications, but exceeding the minimum does not reflect the most economical or efficient choice for typical fuel oil systems. Hence, the specified minimum of 3/8 inch ensures that the system operates within safe and effective parameters.