CIT - Certified Irrigation Technician Certified Irrigation Technician Irrigation Principles and Components 1 — Questions and Answers
Question 1: What is the primary advantage of pressure-compensating (PC) drip emitters over standard drip emitters?
- They are less expensive to manufacture and install
- They deliver a consistent flow rate across a wide range of inlet pressures (Correct answer)
- They require no inline filtration to function properly
- They can be buried at any depth without affecting output
Correct answer: They deliver a consistent flow rate across a wide range of inlet pressures
PC emitters use an internal diaphragm or elastomeric disc to maintain a nearly constant output (typically ±10%) across a broad pressure range (usually 10–50 psi), ensuring uniform application even on sloped terrain or long lateral runs where pressure varies.
Question 2: The Hazen-Williams formula is used in irrigation system design primarily to calculate:
- Evapotranspiration (ET) rates for a given climate zone
- Soil infiltration capacity and percolation time
- Friction loss (pressure drop) in pressurized pipes (Correct answer)
- Sprinkler precipitation rate for a given nozzle
Correct answer: Friction loss (pressure drop) in pressurized pipes
The Hazen-Williams formula is the standard hydraulic tool for calculating friction head loss in pressurized irrigation pipes. Designers use it to size pipes so operating pressure remains within acceptable limits throughout the system.
Question 3: Distribution Uniformity (DU) is a performance metric that measures:
- The ratio of operating pressure to the design pressure of the system
- How evenly water is applied across the entire irrigated area (Correct answer)
- The efficiency of the pump motor under full load
- The percentage of applied water that reaches the root zone without surface evaporation
Correct answer: How evenly water is applied across the entire irrigated area
DU compares the average low-quarter application rate (the driest 25% of the area) to the overall average application rate. A DU of 75% or higher is generally considered acceptable; lower values indicate that some zones are significantly under-watered while others are over-watered.
Question 4: A Reduced Pressure Zone (RPZ) backflow preventer is required in an irrigation application when:
- System operating pressure exceeds 80 psi at the point of connection
- There is a high-hazard cross-connection where contaminants could seriously harm human health if they entered the potable water supply (Correct answer)
- The irrigation system uses only drip emitters rather than spray heads
- The total irrigated area exceeds one acre in size
Correct answer: There is a high-hazard cross-connection where contaminants could seriously harm human health if they entered the potable water supply
RPZ assemblies are mandated for high-hazard cross-connections—such as systems using fertilizer or chemical injection, reclaimed water, or pesticides—because they provide the highest level of protection through two independently acting check valves plus a differential relief valve that opens if either check valve fails.
Question 5: In sprinkler layout design, 'head-to-head coverage' means that:
- All sprinkler heads are installed flush with the finished grade
- Each sprinkler head is spaced so its throw radius reaches the adjacent sprinkler head (Correct answer)
- Pairs of sprinkler heads are installed back-to-back on a common riser
- The arc of each head overlaps the adjacent head's arc by exactly 25%
Correct answer: Each sprinkler head is spaced so its throw radius reaches the adjacent sprinkler head
Head-to-head coverage means sprinklers are spaced so that the radius of throw from each head reaches the center of the next head. This overlapping pattern is the industry standard for achieving adequate distribution uniformity and eliminating dry spots between heads.
Question 6: When sizing a lateral irrigation pipe, which two factors directly determine water velocity inside the pipe?
- Soil texture and the sprinkler arc setting
- Flow rate (GPM) and the pipe's internal diameter (Correct answer)
- Static water pressure and elevation of the water source
- Emitter spacing and the irrigation scheduling interval
Correct answer: Flow rate (GPM) and the pipe's internal diameter
Velocity is calculated as flow rate divided by the pipe's cross-sectional area, which is determined by its internal diameter. Industry best practice limits velocity to 5 ft/sec or less to minimize friction loss, reduce noise, and prevent water hammer damage to pipes and valves.
CIT - Certified Irrigation Technician Certified Irrigation Technician Irrigation Principles and Components 1
What is the primary advantage of pressure-compensating (PC) drip emitters over standard drip emitters?