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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:

 
Design
 
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!
 
Sprinkler Types
 
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
 
Automatic Timers
 
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.
 
Application Rate & Uniformity
 
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

 
Sprinkler Maintenance
 
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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