Grade 3 Water Distribution Practice Questions

What is the main purpose of a cross-connection control (backflow prevention) program?

• ATo maintain adequate system pressure
• BTo prevent contaminated water from flowing back into the potable system
• CTo reduce water main breaks
• DTo control disinfection byproducts

How many gallons are contained in 500 feet of 8-inch diameter pipe?

• A130.6 gal
• B653 gal
• C1,306 gal
• D2,611 gal

What causes water to flow through a distribution system pipe?

• AGravity alone, in every case
• BA difference in pressure (or hydraulic head) between two points
• CThe color or material of the pipe
• DThe age of the water in the pipe

A pressure gauge reads 65 psi at a hydrant. What is the equivalent height of water (feet of head)?

• A28 ft
• B65 ft
• C150 ft
• D325 ft

What is the commonly required minimum horizontal separation between a new water main and a sanitary sewer main?

• A1 foot
• B10 feet
• C50 feet
• D100 feet

A water tower holds water at an elevation of 120 feet above a service connection. What is the approximate static pressure at the connection?

• A43 psi
• B52 psi
• C120 psi
• D277 psi

After a water main repair, what is the standard next step before returning the main to service?

• AImmediately return it to service
• BFlush and disinfect the main, then confirm safe bacteriological sample results
• CAdd fluoride only
• DIncrease system pressure

What is the main advantage of an elevated storage tank compared to a ground-level reservoir?

• AIt is always cheaper to build
• BIt provides system pressure through gravity without a pump running continuously
• CIt doesn't need to be disinfected
• DIt always holds more water than a ground-level tank

Water flows through a 12-inch diameter main (cross-sectional area ≈ 0.785 ft²) at 1,000 gpm. What is the approximate velocity?

• A1.4 ft/s
• B2.8 ft/s
• C5.7 ft/s
• D11.3 ft/s

In a centrifugal pump, what component imparts velocity to the water before it is converted to pressure?

• AThe volute
• BThe impeller
• CThe packing gland
• DThe check valve

A new water main holds 45,000 gallons. Disinfecting it requires a dose of 50 mg/L. How many pounds of chlorine are needed?

• A1.9 lbs
• B9.4 lbs
• C18.8 lbs
• D37.5 lbs

Customers report reddish-brown discolored water after a main break repair in an old, unlined cast-iron main. What is the most likely cause?

• AManganese bacteria
• BIron corrosion products (rust) disturbed by the repair
• CExcess fluoride
• DLow chlorine residual

A 500,000-gallon storage tank serves an area with an average daily demand of 250,000 gallons. What is the tank's turnover time?

• A12 hours
• B1 day
• C2 days
• D4 days

Which backflow prevention assembly protects against both backpressure and backsiphonage, and is required for high-hazard cross-connections?

• AAn air gap or reduced pressure zone (RPZ) assembly
• BA single check valve
• CA pressure-reducing valve
• DA water meter

A 500-foot section of 8-inch main (cross-sectional area 0.349 ft²) needs to be unidirectionally flushed at a velocity of 2.5 ft/s to be effective. What flow rate (gpm) is needed?

• A98 gpm
• B196 gpm
• C392 gpm
• D784 gpm