Distribution System Operation and Maintenance
What a candidate must know
Distribution knowledge centers on pressure, storage, and hydraulic behavior. Understand the minimum and typical operating pressure ranges, how elevation changes affect pressure (about 0.433 psi per foot of water), and why pressure below atmospheric allows intrusion. Know storage types (elevated, ground, hydropneumatic) and the purpose of cycling tanks for demand equalization and fire flow. Study valves: isolation valves, check valves, pressure-reducing and pressure-sustaining valves, and air-release and vacuum-relief valves. Learn main installation and repair practices, tapping, disinfection of new mains, and the importance of keeping systems looped rather than dead-ended to avoid stagnation. Understand cross-connection control and backflow prevention (air gap, RPZ, double check), and the water loss concepts of real versus apparent losses.
Traps
Questions often test the conversion between head and pressure in the wrong direction, or imply that a check valve protects against backsiphonage (it does not; an air gap or RPZ is required). Another trap: assuming higher pressure is always better, when excessive pressure increases leakage and main breaks.
Rule of thumb
Remember 1 psi equals about 2.31 feet of water, so a 100-foot elevation rise costs roughly 43 psi. Worked example: a tank water surface sits 150 feet above a service connection; static pressure is 150 / 2.31, about 65 psi, before friction losses.