Water Distribution Operator Class I flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Specific capacity

Well pumping rate in gpm divided by drawdown in feet; it indicates well efficiency and declines as the well or aquifer degrades.

Looped distribution layout

A grid of interconnected mains that lets water reach any point from two directions, reducing head loss and preventing stagnation.

0.433 psi per foot

Conversion factor stating that each foot of water column exerts 0.433 psi, so 100 feet of elevation creates about 43.3 psi.

Cone of depression

The funnel-shaped lowered water table surrounding a pumping well; overlapping cones from nearby wells indicate interference and reduced yield.

Thrust restraint

Blocks, rods, or restrained joints that resist the unbalanced force at bends, tees, reducers, and dead ends in pressurized mains.

Air release valve

Installed at high points to vent accumulated air that would otherwise reduce capacity and cause erratic flow or water hammer.

Hazen-Williams C factor

A roughness coefficient used in the head loss formula; higher values mean smoother pipe and lower values mean older, rougher mains.

Corporation stop

A valve installed directly on the water main to connect a service line; it is operated with a special key from the surface.

Hydrostatic test

Pressure test of a new main at 1.5 times working pressure, minimum 150 psi, held two hours to check leakage before acceptance.

AWWA C651

Standard practice for disinfecting new water mains, typically 50 mg/L chlorine for 24 hours, followed by flushing and coliform sampling.

Unidirectional flushing

Flushing in one direction at 2.5 to 5 ft/s with valves sequenced to scour biofilm and sediment from a specific main segment.

Net positive suction head

The absolute pressure margin at the pump suction; if available NPSH falls below required NPSH, cavitation damages the impeller.

Affinity laws

For a given pump, flow varies with speed, head with speed squared, and power with speed cubed; used to predict speed or impeller changes.

Altitude valve

A float-controlled valve at elevated storage that admits water when the tank level drops and closes when the tank is full.

Pressure zone

A portion of a distribution system bounded by pressure-reducing valves or booster pumps so pressures stay within 40 to 80 psi.

CT value

Disinfectant concentration in mg/L multiplied by contact time in minutes; used to demonstrate inactivation credit for pathogens.

Nitrification

Biological oxidation of ammonia to nitrite and nitrate in chloraminated systems, consuming chlorine residual and degrading water quality.

DPD method

A colorimetric field test that measures free and total chlorine residual using a reagent that turns pink in proportion to chlorine present.

Water age

The average time water resides in the distribution system; high age from oversized mains and dead ends causes residual loss and byproduct formation.

Air gap

The only absolute backflow protection: a physical separation between the potable supply outlet and the receptor's flood level.

Reduced pressure zone

A testable backflow assembly with two check valves and a relief valve, used for high-hazard connections such as chemical or irrigation lines.

Backsiphonage

Backflow caused by negative or reduced pressure in the supply line drawing nonpotable water into the potable system.

Double check valve assembly

A testable two-check assembly providing backflow protection for low-hazard cross-connections such as commercial boiler feed or nonchemical connections.

Permit-required confined space

A space with limited entry that contains a hazardous atmosphere, engulfment risk, or other serious hazard, requiring an entry permit and attendant.

Boil water advisory

A public notice issued when pressure drops below 20 psi or contamination is suspected, telling customers to boil water before drinking.

Lockout/tagout

Isolating and locking energy sources, such as electrical disconnects and valves, before maintenance to prevent unexpected startup or release.

Maximum contaminant level

The highest allowable concentration of a regulated contaminant in drinking water, enforceable under the Safe Drinking Water Act.

Lead action level

The 90th-percentile lead concentration of 0.015 mg/L that triggers corrosion control, public education, and tap sampling requirements.

Consumer Confidence Report

An annual water quality report delivered to customers by July 1 that lists detected contaminants, sources, and health effects.

Detention time

Volume of a tank or pipe divided by the flow rate through it; units must match, such as gallons divided by gallons per minute.

Pounds formula

Pounds per day of chemical equals concentration in mg/L times flow in MGD times 8.34, the weight of one gallon of water.

Pipe volume factor

Gallons per foot of pipe equals 0.0408 times the inside diameter in inches squared; used for chlorination and flushing volumes.