Water Distribution
Pressure, head, and flow
Convert between pressure and head constantly: 1 psi equals 2.31 feet of water. System pressure comes from elevation, primarily storage tanks, plus pumps. Friction loss rises with flow and with pipe roughness, which is why a lower Hazen-Williams C-factor means a rougher, lossier main. Velocity and detention time matter as much as pressure: an oversized main or a long dead end delivers low chlorine residual even when pressure is fine.
Water quality in the pipes
Chlorine residual decays with time, temperature, and pipe condition. Dead ends, low-demand areas, and poor tank turnover create long detention times, lost residual, and nitrification in chloraminated systems. Flushing, storage tank mixing and turnover, and valve or looping changes are the standard remedies.
Cross-connections
An air gap is the only fail-safe backflow protection. Reduced-pressure zone, double check, and pressure vacuum breaker assemblies serve specific hazard levels and require annual testing by a certified tester.
Traps
Do not swap psi and feet of head. Do not assume a larger main is always better; it can lower velocity and lengthen detention time. Do not confuse static pressure with flowing (residual) pressure, and remember that a backflow test is annual and device-specific.
Worked example
A tank with a 100-foot water surface sits above a service connection. Static pressure at the base is 100 / 2.31 = 43 psi, before subtracting friction loss in the piping. Conversely, a 65-psi reading at a hydrant equals about 150 feet of head.