Distribution System Operations and Maintenance
What to know
Distribution keeps treated water safe from plant to tap. Candidates must understand pressure management (maintaining minimum and maximum pressures), storage tank operation (fill/draw cycles, turnover, mixing, and preventing stagnation), cross-connection control and backflow prevention (air gaps, RPZ devices, vacuum breakers), and main flushing (routine, directional, and after main breaks). Know the causes of discolored water (iron/manganese sediment, biofilm, corrosion products) and the meaning of water age - older water loses residual disinfectant and can grow biofilm. Understand main break response: isolate, repair, flush, disinfect, sample, and restore pressure. Recognize the role of valves, hydrants, and meters in O&M, and the importance of asset records and mapping.
Traps
Questions often imply that higher pressure is always safer - excessive pressure increases leak and break risk. Another trap: treating a main break repair as complete once water flows; disinfection and sampling are required. Watch for confusing backflow prevention with cross-connection identification - you prevent backflow to control a cross-connection.
Worked example / rule of thumb
After a main break, the sequence is isolate → repair → flush → disinfect → sample → return to service. Rule of thumb: keep water moving - stagnation drives residual loss, biofilm, and complaints. Storage turnover and routine flushing are the tools.
Study tip
Build a mental checklist for main breaks and for new main commissioning; they share disinfection and sampling steps.