I am working on a project for an amazing hot springs project in CA. As part of this project, the county is requiring that we provide our own fire suppression water. We have 3 tanks of 40,000gal each. These tanks will equally feed into a 6" PVC pipe. From the tanks, the 6" pipe will drop 172' of elevation, and run approx. 1400' with several bends and a few 90degree turns, terminating at a fire hydrant. The county has given us certain flow requirements which will be physically tested once the system is in place. I need to estimate the flow at that hydrant before we install this expensive pipe. If the estimate is considerably over our requirements, then I feel confident enough to begin the installation. If the estimate is close or below....then I have a problem. I understand the equations for determining flow, BUT they always need numbers that I don't have- specifically velocity! I know my pipe diameter (6"), but how can I estimate velocity? To find velocity I need flow, lol. And so on. Any help would be immensely appreciated!
Tanks- 3 tanks x 40,000gal = 120,000gal
Tank height to top= 20'
Pipe Interior Diameter= 6"
Elevation from Tanks outlet to Hydrant= 172'
Pipe length= 1400' (including approx. 5 x 45deg turns, 2 x 90deg turns)