Water Distribution Operator Class II cheat sheet

Safe yield of a groundwater basin equals long-term recharge minus unavoidable discharge; withdrawal exceeding safe yield causes water-level decline and possible land subsidence.

The hydrologic cycle components: precipitation, evaporation, transpiration, runoff, infiltration, and groundwater recharge; a watershed is the land area draining to a common point.

Design period for water systems typically 20–50 years; peaking factors: maximum day demand 1.5–3.0 × average day, peak hour 2.0–4.0 × average day.

Source water assessment: evaluate quantity, quality, reliability, and vulnerability; springs and infiltration galleries require protection from surface contamination.

Surface water intake design: locate to avoid sediment and debris; provide coarse and fine screens; minimum submergence to prevent vortexing.

Groundwater under the direct influence of surface water (GWUDI) requires treatment equivalent to surface water (filtration and disinfection) under the Surface Water Treatment Rule.

Drought management: implement demand reduction, leak repair, conservation pricing, and alternative sources; safe yield may be reduced during drought.

Water rights and permitting: appropriative and riparian doctrines; withdrawal permits specify volume, rate, and beneficial use.

Pipe materials: ductile iron (DI) for high strength; PVC for corrosion resistance; HDPE for flexibility and trenchless installation; asbestos-cement and cast iron are legacy materials.

Valves: gate valves for isolation (not throttling); butterfly valves for throttling and isolation; globe valves for throttling; check valves allow one-way flow; air-release valves vent trapped air at high points.

Fire hydrants: spacing typically 300–600 ft (100–200 m) in residential areas; flow test to determine available fire flow; drain holes must be clear to prevent freezing.

Service lines: corporation stop at main, curb stop at property line, meter; meter sizing based on fixture units and peak demand.

Thrust restraint: at bends, tees, reducers, and dead ends; use thrust blocks, restrained joints, or tie rods; thrust force = 1.57 × pressure × diameter² (for 90° bend, F = 1.41 × P × A).

Pipe bedding and backfill: compacted bedding to support pipe; select backfill free of rocks and debris; proper compaction under haunches.

Appurtenances: blowoffs at low points, air valves at high points, pressure-reducing valves (PRV) where pressure exceeds limits, and meters for flow measurement.

Water main depth: below frost line; minimum cover typically 3–6 ft depending on climate and traffic loads.

Pump affinity laws: flow (Q) varies directly with speed (N); head (H) varies with N²; power (P) varies with N³.

Pump curve: head-capacity curve slopes downward; operating point is intersection of pump curve and system curve; best efficiency point (BEP) is where efficiency is highest.

Cavitation: caused by insufficient net positive suction head available (NPSHA) versus required (NPSHR); symptoms include noise, vibration, and pitting; remedy by increasing suction pressure or reducing suction lift.

Centrifugal pump priming: required before operation; self-priming pumps or vacuum priming; never run dry.

Motor protection: overload relays, thermal protection, and proper voltage; check rotation before coupling; alignment of pump and motor to prevent vibration and bearing wear.

Pump station design: redundant pumps (lead/lag/standby), surge protection (check valves, surge tanks, air vessels), ventilation, and sump design to avoid vortices.

Variable frequency drives (VFDs) control pump speed to match demand, saving energy; avoid operating near critical speeds.

Maintenance: routine vibration analysis, lubrication, packing adjustment (drip rate 40–60 drops/min for packed pumps), and mechanical seal inspection.

Storage types: ground-level, elevated, and standpipes; elevated tanks provide pressure; hydropneumatic tanks maintain pressure in small systems.

Storage capacity: provide for peak demand, fire flow, and emergency reserve; typical total storage = maximum day demand plus fire flow plus emergency reserve (e.g., 2–3 days average demand).

Tank operation: altitude valve controls fill; check valve prevents backflow; overflow pipe with splash pad; vent sized for air flow; level controls and telemetry.

Hydraulics: pressure = 0.433 psi per foot of elevation (1 psi = 2.31 ft); head loss in pipes via Hazen-Williams: h_f = 10.44 L Q^1.85 / (C^1.85 d^4.87) (US units).

Water hammer: pressure surge due to sudden velocity change; surge pressure = a × ΔV / g (a = wave speed); mitigation by slow-closing valves, surge tanks, air chambers.

Tank mixing and turnover: avoid stagnation; baffles or mixing systems; turnover rate of 2–5 days; monitor chlorine residual and temperature.

Inspection and cleaning: drained inspection every 3–5 years; interior coating inspection; sediment removal; disinfection after cleaning per AWWA standard.

Tank safety: confined space entry procedures; fall protection; corrosion control (cathodic protection, coatings).

CT concept: disinfection efficiency = disinfectant concentration (C) × contact time (T); required CT depends on disinfectant, pH, temperature, and log inactivation.

Chlorine residual: free chlorine (HOCl + OCl-) vs. combined chlorine (chloramines); maintain minimum residual 0.2 mg/L in distribution (free) and 0.5 mg/L (combined) per typical regulations; maximum 4.0 mg/L (free) at entry point.

Chlorine demand: difference between applied dose and residual after contact time; breakpoint chlorination: dose beyond breakpoint yields free chlorine.

Sampling: bacteriological samples in sterile bottles, 100 mL volume, sodium thiosulfate to neutralize chlorine; hold time ≤ 8 hours (or 30 hours if transported on ice); analyze for total coliform and E. coli.

Sampling frequency: based on population served; minimum monthly samples = population/1000 (e.g., 10,000 people → 10 samples/month); repeat within 24 hours if positive.

Water quality parameters: turbidity (NTU), pH (6.5–8.5), temperature, alkalinity, hardness, TDS, and disinfectant residual; monitor for corrosion control (e.g., Langelier Index).

Disinfection byproducts (DBPs): trihalomethanes (THMs) and haloacetic acids (HAAs); formed by chlorine reacting with natural organic matter; limits: THM 80 µg/L, HAA5 60 µg/L (Stage 2).

Flushing and monitoring: routine flushing removes sediment and stale water; monitor chlorine residual and pressure; respond to customer complaints.

Backflow: reverse flow due to backsiphonage (negative pressure) or backpressure (downstream pressure exceeds supply).

Cross-connection: any actual or potential connection between potable water and a non-potable source; must be eliminated or protected by an approved backflow prevention assembly.

Backflow prevention devices: air gap (highest protection, physical separation), reduced pressure zone (RPZ) assembly (testable, for high hazard), double check valve assembly (for low hazard), pressure vacuum breaker (PVB) (for backsiphonage only), atmospheric vacuum breaker (AVB) (not for continuous pressure).

Air gap: minimum 2× pipe diameter above flood rim, never less than 1 inch; inspect annually.

RPZ testing: annually by certified tester; check relief valve opens at 2 psi differential; record results.

Hazard classification: high hazard (toxic or health risk) requires air gap or RPZ; low hazard requires double check or PVB.

Thermal expansion: backflow preventers with check valves create closed system; install thermal expansion tank on water heater.

Survey and enforcement: periodic cross-connection surveys; maintain records; educate customers; ordinance authority for disconnection.

Main repair: isolate section with valves, depressurize, excavate, cut out damaged pipe, install repair clamp or new section; disinfect repaired section before return to service.

Disinfection of new mains: flush, fill with chlorinated water (25–50 mg/L) for 24 hours, flush, then bacteriological sample; AWWA C651 standard.

Tapping: use tapping saddle and machine; wet tap under pressure; corporation stop; proper size and thread compatibility.

Leak detection: acoustic listening, correlators, and data loggers; repair leaks promptly to reduce water loss.

Pipeline construction: trench safety (sloping, shoring, trench box); bedding and backfill; compaction testing; thrust restraint; pressure testing (1.5× working pressure, minimum 1.5 hours).

Service line repair: locate curb stop, excavate, replace section; use repair couplings; flush and disinfect before restoring service.

Preventive maintenance: valve exercising program (annual), hydrant flushing and inspection, main flushing, and corrosion control monitoring.

Record keeping: as-built drawings, repair logs, and asset management; schedule repairs based on condition assessment.

Confined space entry: permit required; test atmosphere for oxygen (19.5–23.5%), flammables (<10% LEL), and toxics (H2S <10 ppm); ventilate; attendant and rescue plan.

Trenching safety: protective system required for trenches ≥5 ft deep; spoil pile at least 2 ft from edge; ladder every 25 ft; inspect daily.

Hazard communication: Safety Data Sheets (SDS) for chemicals (chlorine, fluoride, lime); labeling; training; PPE.

Chlorine safety: use respiratory protection, never add water to acid; store cylinders upright and secured; leak detection.

Regulations: Safe Drinking Water Act (SDWA), National Primary Drinking Water Regulations (NPDWR), Total Coliform Rule, Surface Water Treatment Rule, Lead and Copper Rule, Disinfection Byproduct Rules.

Operator certification: required by state; continuing education; Class II operator responsibilities include system operation, maintenance, and compliance.

Consumer Confidence Report (CCR): annual water quality report to customers by July 1; includes source water, contaminants detected, and health effects.

Recordkeeping and reporting: maintain monitoring records, operation logs, and submit compliance reports to primacy agency; report violations.