I read with interset about your going to 3 1/2" line. When I joined the department I am in we had 3" supply line with 2 1/2" couplings. We loaded it with 1000', and a divider with 500' on either side. This was so we could lay siamese 3" lines, of which the flow at the time was just as feasible as 4" and less expensive. A lot more hose on the ground though. In 1986 we replaced two pumpers and went to 4" line and fittings and have used this ever since. With the 3" line our SOG was to make sure all outlets on the hydrants were gated so we could theoretically lay 4-3" lines from one hydrant, using 2 gates and a 2 gated steamer "Y". Good luck as Chief.
David, welcome to the Nation. I am glad you dropped in to join the group. Dont be shy just jump in anywhere and get your feet wet. There is lots to do, read and be involved with. Your participation and involvement is important to us all. Takes a bit to kinda figure it all out but you will be glad you did. Have fun and look around.