| Sprinkler Systems
A sprinkler system can be a convenient and valuable tool
when irrigating your landscape. However, if used improperly, it results
in substantial amounts of water waste. Click on the topics below to learn
more about your sprinkler system and how you can design, operate and maintain
it more efficiently:
Plan your landscaping before you put the pipe in the
ground. Where are your lawn areas going to be? Where will your shrubs, trees
and flowers be? Make sure you place plants with similar watering needs together--this
is called "hydrozoning". When you turn on a valve to water your grass, you
don’t want your low water-use shrubs to receive the same amount of water.
Not only do you need the same plant types in each watering zone, but
you also need to have the same sprinkler heads. Never install a spray
head and a rotor head
on the same valve. Different head types put out very different amounts
of water in the same time period. If you have mixed heads in the same
zone, you will need to over-water certain areas to get sufficient water
to the entire zone.
Talk to certified professionals in the landscaping and
irrigation businesses. Sprinkler manufacturers’ websites are a great resource
when designing your system. Information ranges from spray patterns to
pressure specifications to winterizing your system!
There are many varieties of sprinkler heads, but
three general categories are: spray, rotor,
and drip.
Spray heads
Spray heads either pop-up out of the ground or have a stationary head.
Spray heads are most commonly used on small areas; turf, shrubs or flower
beds. There are heads designed to spray in all different patterns – depending
on the area to be watered. The most common spray patterns are full, half
and quarter circles. Some heads are adjustable to a wide variety of angles.
In addition to circle patterns, spray heads can also spray rectangle and
square patterns>
Spray heads put out a lot of water in a short amount of
time. This means they have a high application
rate. There is a large range of precipitation rates for different
types and brands, but the average output is 1.5 to 1.7 inches per hour.
Spray heads work well on flat surfaces and with soils that can absorb
the water quickly, such as sand. If spray heads are used on steep slopes
or with a clay soil, the watering times should be cycled to allow the
water to infiltrate into the soil instead of running off onto the street.
Rotor heads
Rotor heads come in two main styles: stream (driven by a gear) or impact.
They are useful in covering large areas, and typically apply water more
uniformly than spray heads. Rotors can spray in full or part circle patterns,
and some brands are adjustable to a wide variety of angles. The application
rate of a rotor is usually lower than that of a spray head. Typical values
are 0.6 to 0.8 inches per hour. This slower output allows them to be used
on all soil types with less cycling.
Drip systems
Drip systems have become popular for irrigating non-turf areas. A drip
system usually consists of a special tube or hose with holes or emitters
along it. These emitters may be spaced with a fixed distance to cover
uniform, closely spaced beds, or randomly to only water certain plants.
Drip irrigation can save time and money when installed properly. It
applies water directly to the soil, eliminating over-spray onto roads
and driveways. The output of drip systems can vary significantly, anywhere
from 0.5 to 24 gallons per hour. S
An automated sprinkler system can help you water efficiently if the timer
is used properly. A study conducted by the Division of Water Resources
found that residents with automatic sprinkler systems in Salt Lake City
typically water 44% more than the lawn needs. Make sure you use your timer
wisely by doing the following:
- Adjust your watering schedule to the season. Your landscape
needs much less water during the spring and fall than it does during
the summer.
- Water only between 6 pm and 10 am. Not watering during the
hot daytime hours will reduce the amount of water you lose to evaporation.
- Don’t water during or after a rainstorm. Historically, Mother
Nature has provided about 30-40% of the moisture your lawn needs to
remain healthy--take advantage of this gift and help conserve our water
resources.
- Program your timer to cycle watering events. Clay type soils
and areas with mild or steep slopes usually can not absorb water fast
enough to prevent it from running off. If such conditions exist in your
landscape, program your timer to water for several shorter periods,
with about an hour in-between, to let the water soak into the soil.
- Keep the battery in your timer fresh and a copy of your schedule
nearby If the power fails and your battery is dead, you will lose
all the adjustments you have made. Just in case, keep a copy of the
schedule that works best for your landscape nearby so you can easily
reprogram the timer if needed.
Read your user’s manual to learn more about
the capabilities of your timer. If it cannot do what you need it to, purchase
a new one. And remember, your timer is there to help you water efficiently,
but it can only do so if you know it well!
If you want to know how long you should water each zone in your landscape
and whether or not you should cycle, use the customized
guide to get you well on your way.
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| Application Rate & Uniformity
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Knowing the rate at which your sprinkler system
applies water (application rate) and assuring that this application is
as uniform as possible is essential if you want to conserve water outdoors.
Application Rate
The Application Rate
(AR) is the amount of water your sprinklers apply per hour. TheAR
can vary substantially, from 0.1 inch per hour (in/hr) to over 3 in/hr.
These variances can occur from one zone to the next. The following table
illustrates the importance of precipitation rate in determining how many
minutes each zone should be watered.
| Zone |
Water
Requirement |
divided
by |
Application
Rate |
multiplied
by |
Conversion
Factor |
equals |
Watering
Time
(adj. for uniform.) |
| 1 |
1
inch |
/ |
0.5
in/hr |
* |
60 |
= |
120
minutes |
| 2 |
1
inch |
/ |
2.0
in.hr |
* |
60 |
= |
30
minutes |
| Example
adapted from: The Irrigation Association, Landscape Irrigation
Auditor Training Manual, 2nd ed., 1996. |
Distribution Uniformity
Distribution Uniformity
(DU) is the measure of how evenly the sprinkler system applies water
to the landscape. A zone with a 50% DU would need twice as much water
applied to it as necessary in order to cover all areas with enough water.
This is one of the primary reasons we over-water. The following table
illustrates how various DUs influence how many minutes zones 1 and 2 from
the previous example need to be watered in order to assure all areas receive
sufficient water:
| Zone |
DU |
Watering
Time |
divided
by |
D.U.
Factor |
= |
Watering
Time
(adj. for uniform.) |
| 1 |
70% |
120
minutes |
/ |
0.7 |
= |
171
minutes |
|
50% |
120
minutes |
/ |
0.5 |
= |
240
minutes |
|
30% |
120
minutes |
/ |
0.3 |
= |
400
minutes |
| 2 |
70% |
30
minutes |
/ |
0.7 |
= |
43
minutes |
|
50% |
30
minutes |
/ |
0.5 |
= |
60
minutes |
|
30% |
30
minutes |
/ |
0.3 |
= |
100
minutes |
| Example
adapted from: The Irrigation Association, Landscape Irrigation
Auditor Training Manual, 2nd ed., 1996. |
How do I determine the Precipitation Rate and Uniformity?
You will need to perform a simple audit of each watering zone in your
landscape to determine the PR and DU. For a simplified guide, see Pecipitation
Rate and Uniformity in our glossary. Or, if you would prefer to have a
certified auditor come to your home and perform an audit, check out the
following resources:
Learn how to do a simple irrigation audit
It is important to do a regular maintenance check
on your sprinklers. If sprinklers are not kept in good working condition,
they can waste water as well as have detrimental effects on your landscape.
Turn on your sprinklers during daylight hours to inspect the system for
broken, clogged or misaligned heads. Print out the Sprinkler
Maintenance Checklist for some tips of what to look for.
A common problem with sprinkler systems is pressure. Without correct
pressure, your sprinklers will not be able to perform as designed. You
may notice large brown areas of lawn where the sprinkler is not reaching,
or shooting over. High pressures can also damage nozzles and heads–sometimes
even causing them to break off. Spray heads should be operating at about
25 to 30 PSI, rotor heads 30 to 50 PSI. You may need a landscape or sprinkler
professional to check the pressure at your sprinkler heads. If your pressure
is too high, pressure-reducing valves and heads may be installed, or you
may be able to retrofit your existing heads with new nozzles instead of
replacing them. Also, consult your manufacturer’s instructions and specifications
to ensure proper pressure.
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