Sports Field Irrigation Design – Part 2

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• Intro/TOC
• Velocity: 5 Foot Per Second (FPS) Rule
• Pressure Surges & Water Hammer
• Fittings & Thrust Blocks
• Gasketed vs. Solvent Weld: Which Is the Best?
• Thrust Blocks

0:00 – 4:07: Intro/TOC

Review of Part 1 (1:42)

Additional information: resources from the Irrigation Association and other sources (2:49):

• Irrigation, Sixth Edition
• Principles of Irrigation
• Designing, Operating, and Maintaining Piping Systems Using PVC Fittings by Ron D. Bliesner
• Handbook of Technical Irrigation Information (Hunter Industries)
• Professional Turf Manager's Efficient Irrigation Practice (Rain Bird)

4:08 – 9:03: Velocity: 5 Foot Per Second (FPS) Rule

Velocity and pressure: review of frictional loss charts (4:08)

5 FPS second rule: Basic hydraulics teaches us that water should travel no faster than 5 feet per second to control pressure surges.

Velocity and mass (5:44)

The larger the pipe diameter, the more volume of water and weight it carries.

9:04 – 23:03: Pressure Surges & Water Hammer

Calculating pressure surges and water hammer (9:59)

Factors that create pressure surges and water hammer (10:59):

• Operating pressure
• Velocity
• Length of pipe
• Time it takes, in seconds, for a valve to close

Online water hammer calculator

Causes of pressure surges and water hammer (14:37):

• High velocities
• Large volume of water
• Change in direction
• Long pipe runs
• Air trapped in the line
• Valves switching on and off

Additional pipe information such as pressure and burst ratings:

• JM Eagle
• NAPCO Pipe & Fittings
• Spears Manufacturing

Mitigating pressure surges and water hammer (15:57)

• Slow velocities
• Reduce demand
• Increase pipe size
• Install pressure-regulating valves
• Install pressure relief valves
• Install continuous air release valves at high points/end of mainlines

Final benefits of slowing velocities (17:36):

• Slowing the water below 5 fps mitigates pressure surges and water hammer.
• Reduces costly repairs in labor, material, etc.
• Repairs can introduce debris and air into the system, causing more damage to the system.
• Allows for a change in velocities over time.
• Incorrect nozzles installed by maintenance.

Changing velocities over time: issue (18:39)

Changing velocities over time: result (20:01)

Some causes of dry spots, or "donuts" in sports fields:

Poor spacing

Low pressure

Changing velocities over time: solution (20:51)

23:04 – end: Fittings & Thrust Blocks

Gasketed vs. Solvent Weld: Which is Best? (23:04)

Gasketed vs. solvent weld: Installations (23:38)

Gasketed and mechanical fitting require:

• More labor to install
• Thrust blocks against "non-distributed" soil

Solvent weld pipe and fittings:

• Require faster installation and less labor
• Typically do not require thrust blocks

Cost difference: Mechanical fittings may cost three times more than solvent weld.

Sizing thrust blocks (source: EJP) (26:40)

Thrust blocks (48:49)

• Thrust blocks should be installed against undisturbed soil.
• Concrete placed over the top and on both sides of the fitting is not acceptable.
• Stones, bricks, concrete blocks, and wood are not proper thrust blocking material.

Review of how water hammer happens (32:31)

Recap (43:43)