Harlow. How do I size #2 fuel oil piping?

Answer 1

You need to know the flow rate needed, the piping length and the allowable pressure drop, which depends on the suction capacity of your burner pump (unless you are using an auxiliary pump to prime the burner pump.). Typical suction capacity is about 15 inches Hg or 7 psi. The first table in the ref. gives you expected pressure drops for 100 feet of piping of various sizes. Note that colder temperatures will result in greater pressure drops. I don't know the temperature the table assumes but it may be 60F since that is what other data tables on that page assume. Also note the data in the last 2 rows of the table seems inconsistent; I hope you won't need piping this large.