Help with determining appropriate pipe size

[jeff3]

I'm trying to connect water from a city water supply to a residential fire sprinkler system. The pipe needs to be typical black steel, and hydrostatic test results show a static pressure of 48-psi. What size pipe would I need to achieve at least 26-gpm flow? I've calculated friction loss to be about 5.6-psi over a 100-ft length. Thanks in advance.

 

[Travis_King]

How have you calculated friction loss without a pipe size?

26 gpm is pretty low, as is 48 psi. You won't need very big piping to accommodate that flow. Any black steel pipe can handle 50 psi with ease.

It's not what you can "achieve", it's the pressure you need at the end, accounting for pressure drop due to pipe friction. Almost literally any pipe size can accommodate a meager 26 gpm.

For instance, if you NEED 30 psi at the sprinklers, then you need a pipe size that will not reduce the head any lower than that.

Speaking of head, is that 5.6 psi (~13 ft static head) drop accounting for the elevation of the sprinkers?