Water Distribution Operator Class I cheat sheet

Specific capacity (gpm per foot of drawdown) = pumping rate ÷ (pumping water level − static water level); a declining value signals well fouling or aquifer decline.

Looped (grid) layouts allow two-direction flow, lower head loss, and prevent stagnation; dead-end mains are minimized and flushed routinely.

Static pressure (psi) = elevation head (ft) × 0.433; conversely, head (ft) = psi × 2.31.

Design criteria commonly used: 20 psi minimum residual under peak/fire conditions and 40–80 psi normal service pressure.

Cone of depression is the drawdown funnel around a pumping well; overlapping cones from adjacent wells indicate interference and reduced combined yield.

A sanitary survey is an on-site evaluation of source, treatment, storage, and distribution to identify sanitary defects before they cause contamination.

Source protection measures include wellhead protection areas, set-back distances from contamination sources, and watershed control for surface supplies.

Surface water supplies require watershed protection, intake screening, and full conventional treatment (coagulation, sedimentation, filtration, disinfection).

Ductile iron (AWWA C151) suits high pressure and restrained joint service; PVC (AWWA C900/C905) resists corrosion; fused HDPE is used for trenchless and directional-drill work.

Gate valves are for isolation, butterfly valves for large mains, check valves prevent reversal, air-release valves go at high points, and blowoffs at low points.

Thrust restraint (blocks, rods, restrained joints) is required at bends, tees, reducers, dead ends, and in-line valves; block size depends on soil bearing and test pressure.

Minimum cover is typically 3 ft, increased where needed to stay below the frost line; cover protects against traffic loads and freezing.

Typical Hazen-Williams C factors: new cement-lined ductile iron 130–140, PVC 140–150, old unlined iron 80–100.

Fire hydrants require a drain, breakaway flange or traffic feature, and adequate branch size (commonly 6 in. minimum); spacing follows needed fire flow.

Service line sequence: corporation stop at the main, service pipe, curb stop at the property line, meter, then customer valve.

Design velocities of roughly 2–5 ft/s balance head loss against sediment deposition; oversized mains and dead ends raise water age.

OSHA 1926.652 requires a protective system (sloping, shoring, or shielding) for trenches 5 ft deep or more unless the excavation is entirely in stable rock.

Trenches 4 ft deep or more need a ladder, stairway, or ramp within 25 ft of lateral travel for workers.

New main hydrostatic test: 1.5 times working pressure (150 psi minimum) held 2 hours, with leakage not exceeding the allowable rate.

New main disinfection per AWWA C651: typically 50 mg/L chlorine for 24 hours, then flushing and satisfactory bacteriological samples before placing in service.

Repairs use full-circle repair clamps or stainless steel sleeves; dissimilar metals need dielectric isolation to prevent galvanic corrosion.

Leak detection uses acoustic listening sticks, ground microphones, and correlators; leaks concentrate at joints, corrosion pits, and service taps.

Unidirectional flushing is performed at 2.5–5 ft/s with valves sequenced so scouring flow travels one direction through the target main segment.

Before cutting a main: verify locations, notify the one-call center, isolate and dewater, and disinfect tools and pipe ends during the repair.

The operating point is the intersection of the pump characteristic curve and the system head curve; changing either curve moves flow and pressure.

Affinity laws for a constant impeller: flow varies with speed, head with speed squared, and power with speed cubed.

Available NPSH must exceed required NPSH; falling short causes cavitation, noise, vibration, and impeller damage.

Pump brake horsepower = (gpm × head in ft) ÷ (3960 × pump efficiency); motor size adds a safety margin.

Elevated storage supplies equalization, emergency and fire flow, and pressure through elevation head; a tank 100 ft above a point gives about 43.3 psi.

An altitude valve at elevated storage admits water when tank level drops and closes at full level to prevent overflow.

Pressure zones separated by pressure-reducing valves or booster pumps keep service pressures in the 40–80 psi target range.

Intermittent pump cycling is controlled with hydropneumatic or bladder tanks, variable-speed drives, or adjusted level setpoints.

Chlorine dose = chlorine demand + desired residual; measure free and total chlorine with the DPD colorimetric method.

CT = disinfectant concentration (mg/L) × contact time (minutes); required CT rises with higher pH and turbidity and with lower temperature.

In chloraminated systems, nitrification is monitored with ammonia, nitrite, and heterotrophic plate count data and controlled by pH adjustment, flushing, and blending.

Manage water age by flushing dead ends, looping mains, right-sizing storage, and cycling tank levels.

Stage 2 DBPR limits: TTHM 80 µg/L and HAA5 60 µg/L as locational running annual averages.

A routine coliform-positive sample triggers repeat sampling; under the RTCR, continued positives require a level 1 or level 2 assessment.

Maintain a detectable disinfectant residual throughout distribution; 0.2 mg/L free chlorine is a common target minimum.

Aesthetic problems (taste, odor, color, hardness, TDS) do not always indicate a health risk but drive customer complaints and operational flushing.

Protection hierarchy: air gap is the only absolute method; RPZ for high hazard, double check valve assembly for low hazard, PVB for irrigation without backpressure.

Backsiphonage results from negative or sub-atmospheric supply pressure; backpressure results from a downstream pressure exceeding supply pressure.

Testable backflow assemblies are tested at installation, annually, and after repair or relocation, and are tagged with the test date and results.

Hose bibb vacuum breakers are required on threaded hose outlets to stop backsiphonage from hoses and attached equipment.

Containment protects the public main at the meter or service; isolation protects individual fixtures and processes inside the building.

Thermal expansion in a closed system (check valve or PRV downstream) requires an expansion tank or relief device.

Hazard classification (health versus non-health) determines the minimum acceptable assembly for each cross-connection.

Permit-required confined space entry requires atmospheric testing (oxygen 19.5–23.5%), ventilation, an attendant outside, an entry permit, and a rescue plan.

Chlorine gas is heavier than air and collects at low points; use low-level detection, supplied-air or SCBA, and never enter a chlorine release area unprotected.

Trench spoil and equipment are kept at least 2 ft from the excavation edge; workers never stand under suspended loads.

Traffic control follows the MUTCD, including signage, cones, and high-visibility apparel for flaggers and crews.

Main break response: isolate the break, notify customers, issue a boil water advisory if pressure fell below 20 psi, then flush and obtain satisfactory samples before rescinding.

Lockout/tagout of electrical, hydraulic, and valve energy sources is required before maintenance to prevent unexpected startup or release.

Security measures include locked hatches and vaults, controlled chemical storage, visitor screening, and a current vulnerability assessment and emergency response plan.

Call 811 (one-call) before any excavation to locate underground utilities.

The Safe Drinking Water Act authorizes EPA, or primacy states, to establish and enforce National Primary Drinking Water Regulations.

Terms: MCL is enforceable; MCLG is a non-enforceable health goal; MRDL limits disinfectant; treatment technique specifies a required practice when no MCL exists.

Lead and copper rule: action levels of 0.015 mg/L lead and 1.3 mg/L copper at the 90th percentile, with corrosion control and public education if exceeded.

Disinfectant residual MRDL is 4.0 mg/L; TTHM 80 µg/L and HAA5 60 µg/L are evaluated as locational running annual averages.

The Consumer Confidence Report is due to customers by July 1 each year and lists detected contaminants, sources, and health effects.

Tier 1 public notice must be issued within 24 hours for acute violations such as an E. coli MCL or nitrate exceedance.

RTCR routine coliform sample counts are set by population served, with repeat samples required after any positive.

Monitoring results and related records are generally retained at least 5 years, with some categories (e.g., chemical) retained longer or as the state requires.

Pressure–head: psi = ft × 0.433 and ft = psi × 2.31.

Flow in a pipe: Q (gpm) = 2.448 × d² (in.) × v (ft/s).

Storage or main volume: gallons per foot of pipe = 0.0408 × d² (in.).

Detention time = volume ÷ flow, with matching units (e.g., gallons ÷ gpm = minutes).

Chemical feed: lb/day = mg/L × MGD × 8.34.

Dose from feed rate: mg/L = lb/day ÷ (MGD × 8.34).

Pump horsepower: water hp = (gpm × head ft) ÷ 3960; brake hp = water hp ÷ pump efficiency.

Hazen-Williams head loss (US units): h = 10.44 × L × Q^1.85 ÷ (C^1.85 × d^4.87).

Drawdown = pumping water level − static water level; specific capacity = gpm ÷ drawdown.