sprinkler selection (2)

Sprinkler Selection

Sprinkler Selection

• Spray– Pop-up– Shrub spray

• Rotating– Impulse or Impact– Pop-up Gear driven

• Bubblers and drip irrigation

Considerations

• Goal – select the type that will cover the area properly using the least number of sprinklers

• Windy – low angle• Arid climate – higher flow or multiple

irrigation cycles• Slopes• Soil

Precipitation Rate

• Don’t mix on one valve circuit

• Matched Precipitation Rate Sprinklers (MPR)

• See Rainbird Catalog 18-22 MPR Series

• (Stryker) Look for this feature

Spray Heads

• For smaller areas

• For areas with enclosed borders

• Require tightly controlled spray

• Dense tree growth that would get in the way of rotor spray

• Mixed plantings needing different amounts of water

Spray Heads

• Fixed spray heads

• Fan shaped pattern of water

• Spaced up to 18 feet apart

• Need between 20 and 30 PSI to operate properly

Typical (Standard)

Spray Patterns

GPM Calculation for reduction of Spray heads

• Use the chart

• Actually just reducing the pressure– Example:

30 PSI 15 ft 1.85 GPM

Original

25 PSI 14 ft 1.65 GPM

Modified

Other Spray Patterns

• Specialty Strips– Center – Side– End

• Variable Arc Nozzle– For occasional odd shaped, in between areas– From 0o to 3600

• Stream Spray - fingers of water

Stream vs Fan Sprays

Stream Fan

15-30 PSI (low) 20-30 PSI

5-22 feet (small areas) 5-18 feet

PR - 1/3 – 1 1/2in/hour PR - 1-4 in/hour

slopes, tight fine grain soils

Rotors

• Rotating streams of water• Impact rotors – fire bursts of water• Gear Driven rotors

– very quiet– lower maintenance– smaller in size

• Multi-stream rotors – expensive, much higher maintenance

Rotors

• Spacing – 18 – 55 feet apart• 5 – 100 gpm• PR – ¼ - 2 in/hour• Require more water pressure to operate than

spray heads• (Stryker) water pressure at the head must

exceed the distance between heads– If you want 35 feet apart, be sure 35 PSI

Rotors - warning

• (Stryker) Don’t rely on manufacturers’ radius on charts

• If less than 6 GPM, maximum spacing should never be more than 35’ between sprinklers

• (Stryker) They don’t test with wind

Rotor selection

• Select the appropriate Nozzle size for each rotor to match the precipitation rates

• The rotation speed is the same regardless of whether the rotor is adjusted to a full circle or a quarter circle

• If a quarter circle, passing over the same area 4 times in the same amount of time as 1 full circle

Rotor Precipitation Rates

• If the nozzle is the same the quarter circle will put down 4 times as much water on the area as a full circle

• To match: change the nozzle to cut the amount of water to ¼

• Half circle – nozzle with ½ amount of the water of a full circle, etc.

• See Rainbird catalog pg. 74 & 75

Rotor adjustment

• If you adjust the radius you need to adjust the nozzle too

• (Stryker) Don’t use rotors with nozzle flows less than 2.5 GPM except in corners (1/4 circle)

GPM Calculation for reduction of Rotor heads

• GPM stays the same– Doesn’t change the amount of the water coming

out of the nozzle– Use the pin to reduce the radius– Uneven water, dry spots– Should be reducing the GPM too, but you don’t

• Only use the radius adjustment screw on rotors when nothing else will work

Stryker’s Cheat Chart – Rotors20-29’ Spacing

¼ circle 30 PSI .8 GPM

½ circle 30 PSI 1.6 GPM

¾ circle 30 PSI 2.4 GPM

Full Circle 30 PSI 3.2 GPM

Stryker’s Cheat Chart – Rotors30-39’ Spacing

¼ circle 40 PSI 1.5 GPM

½ circle 40 PSI 3.0 GPM

¾ circle 40 PSI 4.5 GPM

Full Circle 40 PSI 6.0 GPM

Stryker’s Cheat Chart – Rotors40-55’ Spacing

¼ circle 55 PSI 3.0 GPM

½ circle 55 PSI 5.5 GPM

¾ circle 55 PSI 8.0 GPM

Full Circle 55 PSI 11.0 GPM

How to decideSpray Rotor

Up to 18 feet apart 18-55 feet apart

More sprinklers, more trenching

Less trenching

Less per sprinkler Costs more per sprinkler

Lower PSI Need 40 PSI minimum

City Water Irrigation Water

Body Styles

• Pop-up– Installed below ground– Available 3”, 4”, 6” 12” above ground

• Need to clear the lawn height

• Shrub style– On a ‘riser’– Use away from traffic patterns

• Cost the same

Metal or Plastic

• Metal is more durable

• Until 1970’s, metal was preferred material

• Now plastic is the most common

• Metal too expensive

• Some have a brass fitting

• (Stryker) not much difference today

What to look for• Spring retraction

– Use a spring to pull the pop-up riser down into the case

– Stay away from gravity retraction

• Wiper Seal – soft plastic seal around the pop-up riser stem that seals the riser wo it won’t leak– Keeps the dirt out

• 3” pop-up height or higher– Most pros use 4” in lawn areas and 6”-12” in

shrub areas

Pressure Requirements• Spray Type

– (Stryker) When designing, use 30 PSI unless you know that it is lower

– If the pressure is lower, place sprinklers closer together

• Rotor Type– Won’t work well with less than 30 PSI

• Drip Emitters– Usually best at around 20 PSI

Mix and Match

• Don’t mix and match on the same valve

• Special valve to reduce the pressure for the lower pressure sprinklers

• Design for the high pressure

Trajectory of Water• As water comes out of the sprinkler head, it travels in a curved

path through the air to the ground.. Trajectories of spray include:

• 0 degree trajectory -- this flat spray can be used for throwing water under low shrubs

• 10 degree trajectory -- this low angle spray can be used in a high wind situation and for shrub and groundcover beds

• 22-26 degree of trajectory -- this is the standard trajectory thrown by most sprinklers

• 30-35 degree trajectory -- this is a special trajectory used for throwing water over plant material such as groundcovers and gardens