Water Distribution Operator Class III case studies
Water Distribution Operator Class III · Put your knowledge to work in context.
The Water Distribution Operator Class III credential (also called Grade III or D3) is a mid-to-advanced certification for people who operate and maintain drinking water distribution systems - mains, valves, hydrants, service lines, pumps, and storage - rather than treatment plants alone. It is typically pursued by operators who already hold an entry-level distribution certificate and are moving into roles with greater responsibility: complex hydraulic problem-solving, disinfection and cross-connection oversight, larger repair and construction projects, sampling and compliance duties, and crew-level decision-making. The Water Distribution Operator Class III case studies are 5 cases and about 3,149 words.
1Low Pressure at the Top of the Zone After a Main Replacement
A 12-inch cast iron main on Elm Street was replaced with 12-inch cement-lined ductile iron over a 1,400-foot stretch. The old main had a measured Hazen-Williams C of 78; the new main is assumed at C = 140.
661 words, about 3 min2Pump Cycling and a Check Valve That Won't Seat
A booster station has two 250-gpm vertical turbine pumps in a lead/lag arrangement feeding a 3,000-foot transmission main to a 500,000-gallon elevated tank. The lead pump runs on a pressure switch set at 62 psi (on) and 78 psi (off).
652 words, about 3 min3Tank Turnover and Chlorine Decay at a Remote Elevated Tank
A 1.0-million-gallon elevated tank serves a pressure zone with average demand of 0.9 mgd. The tank floats on the system and is refilled by the transmission main whenever system pressure exceeds the tank's float level.
602 words, about 3 min4Coliform Positive After a Water Main Repair
A crew repaired a 10-inch main break on a commercial street at 2 a.m., using a repair clamp after cutting out a 6-foot section. The main was depressurized for about 4 hours.
583 words, about 3 min5Confined-Space Entry to Replace a Valve in a Vault
A 6-foot-deep valve vault on a 16-inch transmission main needs a 12-inch gate valve replaced. The vault is 5 ft × 5 ft, entered through a 30-inch manhole.
651 words, about 3 min