CIT - Certified Irrigation Technician Hydraulics and Water Management 2

Question 1

A sprinkler system mainline has a static pressure of 65 PSI. After opening a zone with four spray heads, the pressure drops to 48 PSI. What is the pressure loss in the system?

Accepted Answer

17 PSI

Answer

Pressure loss is calculated as the difference between static pressure (no flow) and dynamic pressure (during flow): 65 PSI - 48 PSI = 17 PSI. This loss occurs due to friction in pipes, fittings, valves, and the elevation change.

Question 2

According to the Hazen-Williams equation, as pipe diameter increases, friction loss per unit length:

Accepted Answer

Decreases significantly

Answer

As pipe diameter increases, friction loss decreases significantly because the larger cross-sectional area reduces water velocity for the same flow rate. Friction loss is proportional to approximately the 4.87th power of the pipe diameter (inverse relationship).

Question 3

What is the recommended maximum velocity of water flow in irrigation mainline pipes to minimize water hammer and friction loss?

Accepted Answer

5 feet per second

Answer

The recommended maximum water velocity in irrigation mainlines is 5 feet per second (fps). Exceeding this velocity significantly increases friction loss and the risk of water hammer, which can damage pipes, fittings, and valves.

Question 4

A pressure gauge at the base of a hill reads 60 PSI. The irrigation zone at the top of the hill is 46 feet higher in elevation. What is the approximate pressure available at the top of the hill (ignoring friction loss)?

Accepted Answer

40 PSI

Answer

Pressure loss due to elevation change is approximately 0.433 PSI per foot of elevation gain. For 46 feet: 46 x 0.433 = approximately 20 PSI loss. Available pressure at the top: 60 - 20 = 40 PSI.

Question 5

What is the purpose of a pressure regulator in an irrigation system?

Accepted Answer

To reduce and maintain constant downstream pressure regardless of supply pressure fluctuations

Answer

A pressure regulator reduces high supply pressure to a consistent downstream pressure, protecting system components and ensuring proper sprinkler performance. Most residential regulators reduce 80-120 PSI supply pressure to 40-50 PSI for the irrigation system.

CIT - Certified Irrigation Technician Practice Test

CIT - Certified Irrigation Technician Practice Test

CIT - Certified Irrigation Technician Hydraulics and Water Management 2