Operation & Maintenance Flashcards
What factors are considered in sizing customer meters, why is it done and how often should they be tested?
- Pressure at the service connection
- Highest fixture in the building being served
- Any backflow prevention device
- A 5/8 inch meter should be tested every 5 to 10 years
- Meter should not have more than 20 psi of head loss
- One inch and smaller meters shouldn’t exceed 15 psi of head loss
What are the correct procedures to follow in collecting bacteriological samples?
- Routine bac-t samples should be taken at the customer’s tap at various points that represent the entire system
- Sampling bottle/bag should be filled just above the fill line or 1 inch from the top.
- Should allow sample tap water to run for several minutes or as long as necessary to clear the service line
- Sample identification cards (chain of custody) need to be filled out completely
- The sample should be transported as soon as possible in a cool container with an ice pack
What do the following terms represent in reference to water quality: total coliform, fecal coliform, and presence/absence
Total coliform
* A measurement that shows the presence of coliform bacteria in a water system and is an indicator organism
Fecal coliform
* A specific class of bacteria coming from animal intestines
* If sample is coliform positive, a fecal coliform test if performed
What do the following abbreviations stand for and do they mean: gpm, MGD, TTHM, psi, HAA, NTU, and mg/L
- GPM - gallons per minute
- MGD - million gallons per day
- TTHM - total trihalomethane
- PSI - pounds per square inch
- NTU - nephelometric turbidity unit
- MG/L - milligrams per liter or ppm = parts per million are the same
What is the purpose of sanitary surveys, how often are they required and who is authorized to perform them?
- Executive Secretary shall ensure a sanitary survey is conducted at least every THREE years
- Divison of Drinking Water
- DEQ district engineers
- Local health departments
- Forest service engineers
- Utah Rural Water Association staff
- Consulting engineers
- Other authorized by Executive Secretary
What are the aesthetic concerns of drinking water and what do they indicate?
- Taste
- Odor
- Coloration of water
- Things that affect this are extreme hardness or high total dissolved solids
- Hydrogen sulfide causes rotten egg odors
What is the main purpose of a finished water storage reservoir?
- Provides adequate water to the water system during average and peak demands
- Provides adequate pressure throughout the water systems
- Reserve storage
- Fire protection
What would be the appropriate application for the following types of valves: gate valve, air and vacuum relief valve, altitude valve, pressure sustaining valve, butterfly valve, check valve, pressure relief and pressure regulating valve
Gate valve
* Most commonly used in the distribution system, and is either all the way open or all the way closed
* Can be repacked without taking out of service
Air & Vacuum relief valve
* Allow air in & out
* Should be placed at the highest point in the system
Altitude valve
* Regulates tank levels by opening when the system psi drops below a certain pressure and closes when the reservoir reaches a predetermined level
Pressure sustaining valve
* maintain either upstream or downstream pressures depending on the position of the pilot screw
* Help reduce water hammer
Butterfly valve
*Higher resistance to flow
* Used for flow control& isolation
Check valve
* keep flows going in one direction
* Flow must be directional with pump discharge lines, customer service lines, and water treatment plants
What is hardness in water and what chemicals cause it
- Caused by salts of calcium & magnesium (bicarbonate, carbonate, sulfate, chloride, and nitrate
What are chloramines, how often are they formed, and do they have any beneficial use
- Chloramines are a reaction between hypochlorous acid (applied chlorine) and ammonia
- When done intentionally, it can reduce tastes and odors
- Chloramines are a weaker disinfection than chlorine
What is a cross connection, what two types of backflow can cause one, and what methods of protection can be used to prevent them
A connection between a potable and an unapproved source
- Backsiphonage - backflow caused by a negative or below atmospheric pressure in a water system
- Backpressure - when users pressure is higher than the system pressure
Air Gap
* minimum of 1 inch or two times the diameter of the pipe
* safest method of backflow prevention
Double Check Assembly
* has two independent internally loaded check valves, 2 shut off valves, & 4 test cocks
What is a water hammer, how is it caused, and how can it be prevented
Occurs when a valve is closed quickly or a pump shuts down and causes the water pressure to rise and fall rapidly.
Define the following terms: cross connections, back siphonage, back pressure, air gap, double check valve assembly, reduced pressure principle assembly, and pressure vacuum breaker assembly
What causes friction head loss, what factors can affect It, and how does it relate to velocity in pipelines
Energy used up by water movement
Two conditions that affect head loss
* Roughness of the pipe
* Velocity of the water
Two conditions that affect roughness
* Age - condition
* Type of pipe materials
Why do electric motors normally draw more power when starting
- Upon start-up an electric motor will develop a torque to turn the pump shaft and impeller
- Torque causes the motor to draw a high amperage
- Amperage drops once the pump is up to speed
What do the following terms mean in relation to drinking water quality: disinfection, pathogenic, toxic, pH, aesthetic, culinary, and potable
- Disinfection - The process designed to kill pathogenic microorganisms in drinking water
- Pathogenic - Disease-causing organisms
- Toxic - A substance that is harmful to humans if consumed
- pH (potential hydrogen) - A measurement of how acidic or basic a substance is
- Aesthetic - A substance in drinking water that causes a taste, odor, or color that is not harmful to humans when consumed
- Culinary - Water suitable for human consumption
- Potable - Water fit for human consumption
What is pH, how does it affect the distribution of water quality, and on what type of a scale is it measured
A measurement that refers to the basic or acidic conditions of the water
- pH is measured on a scale (Langlier Saturation Index) 0 - 14
- Less than 7 is more acidic, greater than 7 is more basic or higher alkalinity (7 is neutral)
What effect will wear have on meter accuracy over an extended period of time?
- Worn meters will cause the meter to under-register, allowing the customer to receive more water than they pay for
- Over time a worn meter will cost the water system revenue
What is a drain hole used for in a fire hydrant? What is a dry barrel fire hydrant, what does the term hydrant bury refer to and when should flow testing of fire hydrants take place
- Drains barrel to protect from freezing
Dry Barrel
* The operating valve on dry-barrel hydrants is located at the bottom, which makes it possible to empty all the water in the hydrant to prevent any damage that might be caused by freezing.
Hydrant bury
*The distance below the ground to the main connection
Flow testing
* During periods of low demand
What is the relationship between mg/L and ppm; ug/L and ppb
- MG/L - Milligrams per liter (same as ppm - parts per million)
- UG/L - Micrograms/liter or parts per billion
1 ppb = 1 ug/L (also written as ug/l). A measurement of 6 mg/L is the same as 6 ppm or 6,000 ppb, which is equal to 6,000 ug/L.
What is thrust blocking, where is it used, and how does it work
- A concrete mass cast in place between a fitting and the undisturbed soil at the side or bottom of the pipe trench.
- Purpose is to keep fitting from moving & either coming loose or apart from the force of the water pressure in the pipe
- Thrust anchors - used when thrust blocks cannot be used
What is the primary purpose of drinking water storage tanks
- Provides a volume of water to the water system during average and peak demands
- Provides adequate pressure throughout the water systems
- Reserve storage
- Fire protection
What is the C-factor and what does it indicate in a water pipe
- Indicates the smoothness of pipe material
- The higher the C value, the smoother the pipe
- Tuberculation reduces C value
What is wire-to-water efficiency and how is it calculated
The combined efficiency of the pump and the motor together. Also called the overall efficiency
- Water HP/Electrical HP x 100% = overall efficiency
What is a positive displacement type meter; a velocity type meter
Positive Displacement Meters (Most common in water systems)
* Nutating disk - nutating means nodding. When the water flows the disk rotates
* Oscillating Piston - Water flows into a chamber and displaces the piston
*Higher head loss than the nutating disk
Velocity Meter
* Propeller, venturi, insertion type, and most electronic types
*Rotors or propellers are turned by the velocity of a meter
What is unaccountable water loss and what percentage is generally acceptable
- Affected by: leaks, pressures, the efficiency of the meter maintenance, attention given to leak reduction & unauthorized use of water
- In Some systems 10% of the water produced
- Other systems not until 20%
What is a lighting arrestor and what is it used for
- Becomes a low-resistance conductor to ground when the line voltage exceeds a predetermined amount.
- Used to protect equipment from lightning strikes.
- No device made to protect against a direct hit
What would be the correct actions to take in the event a customer calls and complains that the drinking water has made him sick
What type of concerns would be caused by high levels of iron in drinking water
What is DPD used for in the water system and how does it work
What does the membrane filter test analyze with regard to bacteriological sampling
What are the proper sampling techniques for microbiological sampling
What screen size and protection should air vacuum release valves have above and below ground
What is the minimum horizontal distance between a sewer and a water main
What causes electrolysis in a water main
With regards to fire hydrants, what does the term stringing mean
What is the best method for controlling cross connections
When a water main has been installed in a trench, what is the procedure for placing the first layer of backfill
What is a thermal expansion and what are the considerations with regard to backflow assemblies and devices
What type of material would require less surface area when designing a thrust block
