Understanding Pressure Regulation

Note: The following catalog of content covered in this webinar is time stamped to allow you to follow along or skip to sections of the video that are relevant to your questions. You can also search for content on this page using the FIND command in your browser (CTRL + F in Windows, Command + F in Mac OS.)

• Intro / TOC
• What Is a Pressure Regulator?
• The Benefits of Pressure Regulation
• Pressure Regulators for Irrigation Systems
• How Do Regulators Work?
• How and When to Use Pressure Regulation

0:00 – 3:37: Intro / TOC

Irrigation systems are dependent on pressure and flow.

 

For the purposes of this webinar, “regulated pressure” means “regulated dynamic pressure,” meaning the system is on and the water is flowing.

3:38 – 5:59: What Is a Pressure Regulator?

Definition: A pressure regulator is a mechanical device that reduces input pressure to a preset downstream pressure.

 

Regulation vs. Compensation (4:20):

• Pressure regulation: Spring stiffness controls the pressure drop through the device to regulate output pressure.
• Pressure compensation: A flexible cylinder restricts the flow through the device as pressure increases.

6:00 – 12:44: The Benefits of Pressure Regulation

Why use pressure regulation?

Pressure regulation maximizes the lifespan of the system. (6:06)

 

Pressure regulation prevents damage to pipe, fittings, and emission devices.

 

Some products do not function at higher pressures than specified:

• Drip emitters close up.
• Tubing bursts.
• Fittings pop off tubing.

 

Pressure regulation optimizes system efficiency. (7:07)

 

Many products are designed to a set optimal pressure that maximizes their performance and efficiency.

 

Applying this optimal pressure:

• Reduces excessive flow rates
• Reduces misting from overhead devices
• Increases uniformity across the entire zone

 

System comparison of regulated and non-regulated zones (7:55)

We’re used to seeing a large amount of water misting out of a spray nozzle. But that excess water ends up turning into a fine mist that wastes water and causes excessive runoff. Pressure regulation prevents these issues.

 

Pressure regulation balances system performance. (10:30)

Without pressure regulation, it’s common that the first head in a system throws the correct rate and pressure slowly decreases down the line, rather than maintaining a balanced pressure throughout all heads.

 

Question: Is 40 PSI a good pressure for a dripline? (12:07)

Answer: Yes.

12:45 – 17:24: Pressure Regulators for Irrigation Systems

Common pressure regulators (12:45):

Mainline pressure regulators (13:00)

The pressure of an entire property can be regulated at the point of connection using a mainline pressure regulator.

 

Valve pressure regulators (13:30)

Regulating pressure at the valve provides optimal pressure for the entire zone.

• Fixed pressure regulator
• Adjustable regulator
• Drip zone kits

 

Drip zone kits for micro-irrigation systems (14:55)

Micro-irrigation systems require pressure regulation and filtration.

 

Pressure regulated sprays (sprinklers and shrub adapters) (15:30)

Regulating pressure at the sprinkler head allows each nozzle to see the same, optimal pressure for balanced performance.

• Higher uniformity
• Minimal misting
• Lower flow rates

 

Pressure regulated rotors (16:02)

Regulating pressure at the rotor allows each nozzle to see the same, optimal pressure for balanced performance.

• Higher uniformity
• Minimal misting
• Lower flow rates

17:25 – 29:29: How Do Regulators Work?

How it works: Drip zone kit (17:31)

1. Water enters regulator at some inlet pressure.

2. Water flows through the center, attached to a flexible diagram.

3. The spring keeps the flow path open while the diaphragm tries to close it. (Spring stiffness determines the constant outlet pressure.)

 

Pressure vs. flow requirement (18:56)

 

Question: If the available PSI is less than what is allowed to operate a pressure regulator, what is the best approach? (22:55)

Answer: It’s best to have some kind of regulator on the system in case of a surge. If you are absolutely positive that pressure surges won’t occur, you can add a filter. An Accu Sync (available from Hunter) can provide a safeguard against surges, but it also takes about a 15 PSI differential.

 

How it works: Rotors (24:19)

1. Pressure on top of the piston forces the piston and spring downward.

2. Piston begins to close off the gap with the valve.

3. The piston closes the gap until the upward force of the spring equals the downward force of the piston.

 

How it works: Pressure regulated sprays (25:03)

• Pressure regulated sprays function the same as pressure regulated rotors
• Back-pressure balances with the regulator spring to set the outlet pressure.
• Pressure differential is needed to start regulation.

 

Pressure differential (25:37)

Pressure regulators require a pressure differential to overcome the spring force and friction of the regulator assembly.

 

Typically, a 10 PSI differential is required.

 

Question: Should pressure-regulated heads be mixed with non-regulated heads in the same zone? (27:45)

Answer: They can be mixed if necessary in a retrofit application, but it’s not recommended in a new design.

 

Question: Is it possible to use a shut-off valve to reduce pressure? (20:19)

Answer: No, a shut-off valve is meant to be an all-or-nothing application – on or off. It shouldn’t be used partially open.

 

Question: With a rate of 45 PSI downstream of the valve, is it better to not use the PRS40? (28:59)

Answer: No, in this case, you wouldn’t need to use pressure-regulated heads.

29:30 – end: How and When to Use Pressure Regulation

Dynamic pressure (29:30)

• For each zone, determine: size of area, irrigation product type, and quantity of devices.
• Find available working pressure for the system.
• Tailor dynamic pressure to the recommended pressure for the irrigation devices.

 

Micro-irrigation systems (30:41)

Drip zone kits come in 20, 30, or 40 PSI options.

 

Choose the appropriate drip zone kit based on available dynamic pressure and expected flow rate.

 

More on micro-irrigation systems (32:05)

A pressure regulator to a drip system provides insurance besides optimizing efficiencies.

 

Overhead irrigation systems (32:47)

• Spray nozzles: 30 PSI
• Rotary nozzles: 40 or 45 PSI
• Rotors: 45 PSI

 

When to use pressure regulation at the head and when to use it at the valve (35:16)

If pressures exceed the recommended pressure by 10% or more, use a regulator to bring the pressure down to the desired amount.

 

Two-step pressure regulation (35:57)

Some overhead systems have regulation at the valve and again at the heads:

• Create beneficial redundancy (safety)
• Protect the zone from high pressures and spiking pressures
• Provide consistent pressure to each nozzle

 

Two-step pressure regulation example (36:34)

Example: Incoming street pressure is extremely high (125 PSI)

• Pressure regulation needed at the backflow (to 80 PSI)
• Another regulator needed at the valve (to 50 PSI)

or

• Pressure regulation needed at the backflow (to 80 PSI)
• Regulators needed at the sprinkler (to 30, 40, or 45 PSI)

 

Summary (37:29)

Pressure regulation devices reduce input pressures to preset output pressures to maximize the performance of irrigation systems in efficiency and longevity.

• At the point of connection, the valve, sprinkler heads, or a combination.
• Pressure differential required.
• Check the specs.

 

Question: If regulating the valve and the head, would I need to make sure that the pressure at the valve is set high enough so the head still pops up? (38:25)

Answer: Yes, definitely. The heads will still pop up unless the system drops down to 12 or 15 PSI. But if you regulate at both the valve and the head, you’ll want to ensure that you have about 50 PSI at those heads. You may want to use an Accu Sync set to 60 PSI at the valve.

 

The importance of setting a sufficient design pressure in an irrigation system (39:35)

 

Methods for testing the pressure in a system after installation, including tee gauges (42:45)

 

Note that Irrigation F/X has a pressure variation factor setting that allows the designer to set the allowed variation in a system. (44:35)

 

As you equalize the pressure across each head, the flow rates will likely drop. (45:30)

 

When working with drip kit valves, pay special attention to the valves’ required pressure rates. (46:27)

 

Question: What is the name of the Hunter tee gauge shown in this webinar? (48:12)

Answer: The assembly that includes the pressure gauge is called the MP Gauge. If you want to use your own pressure gauge, you can use it with the MP Tee. They’re available at your local distributor, or you can contact your Hunter representative.

 

Question: Who would I ask to find out the available pressure on a site? (49:30)

Answer: Generally, the municipality, contractor, or engineer should know. Or you can do your own test using a flow sensor.