Landscape irrigation is responsible for approximately 50% of home water use. Inefficient irrigation practices can waste up to 30% of the water applied, making landscape irrigation an excellent area to examine in trying to find ways to conserve water.

While inspecting irrigation systems lies beyond the scope of a general home inspection under most Standards of Practice, inspectors in certain areas may want to become qualified to perform landscape irrigation audits. Audits involve evaluating irrigation systems and making recommendations related to water conservation.

Landscape plants with Low Water Requirements

Lawns require large quantities of water. Limiting turfgrass to 20% or less of a landscaped area can save considerable amounts of water.

Xeriscape is a method of landscaping which requires little or no supplemental irrigation. Its use is important in areas of the country which have a limited supply of water.

Although some people think of Xeriscape as gravel and cactus, it can actually be lush and colorful.

Colorado Water Wise Council provides information about Xeriscape.

Xeriscape Conversion Study- The Southern Nevada Water Authority (SNWA) and the Bureau of Reclamation funded a comprehensive Xeriscape Conversion Study to research the amount of water saved by property owners who removed grass and replaced it with water-efficient xeriscape.

The final Xeriscape Conversion Study results found that participants saved an average of 55 gallons of water per square foot by converting grass to a water-efficient landscape.

Greywater Systems

Greywater is washwater, including all wastewater excepting toilet waste and food wastes from garbage disposals. Some jurisdictions allow greywater irrigation systems which make use of water which would otherwise be wasted. Storing roof runoff is one method for taking advantage of this possibility.

Low-volume systems

Bubblers, micro-spray and drip systems provide more precise water placement at lower volume, resulting in less energy used to distribute water and less water lost to evaporation, runoff and overspray.

Controllers

Controllers are the computerized brains of automatic watering systems. They determine the watering times and amounts for different zones an open and close valves automatically.

Programmable, weather-based controllers for irrigation systems are available which receive hourly updates from local weather stations and are programmed to make operation decisions based on information about solar radiation, temperature, wind, and humidity.

Programmable, weather-based controllers allow users to program irrigation system operation…

for optimal timing, such as when evaporation rates will be lower
to accommodate changes of season as the number of daylight hours change and as wet or dry seasons approach.
according to the needs of the plants in each hydrozone.
to apply water at a rate at which the soil can absorb it, reducing runoff, erosion and waste.
to operate the system when soil moisture sensors indicate that it’s needed.
to shut down the system during periods of rain or when moisture sensors indicate that irrigation is no longer needed.
some systems have leak sensors which automatically shut down lines which are leaking.
to control water pressure, ensuring uniform irrigation across a large area.

Hydrozones

Hydrozones are sections of an irrigated area in which plants with similar irrigation needs are grouped together to allow for more efficient irrigation practices.

Sensors

Rain sensors are designed to shut down irrigation systems during rainfall and must be mounted in an unprotected area such as a roof edge.
Moisture sensors sense moisture levels in soil and prevent watering until soil is sufficiently dry.
Wind sensors prevent spray irrigation at times when the wind is strong enough to interfere with spray patterns.

Valves

Valves in systems with controllers are opened and closed electrically. Some valves…

shut down when they sense a leaking diaphragm.
provide for low-flow irrigation.
help regulate system pressure. High pressure can waste 6%-8% of water from misting.

Sprinkler Heads

Rotary Sprinkler Heads- are usually used on turfgrass and are available with adjustable spray patterns, low-volume heads, matched precipitation rates and large-droplet nozzles.
Pop-up Spray Heads- are available with different spray patterns, check valves which prevent pipe drainage from low-lying sprinkler heads and low-volume heads.

Irrigation Terms

Water budget- is the amount of water needed to irrigate a landscaped area during the driest season. It takes into account lot size, plant and soil type. The water budget is used to program the controller.

ET Rate- Evapotranspiration rate. This is the rate of soil moisture loss from both evaporation and plant transpiration. Plants transmit water vapor to the air in a process called “transpiration”. Sort of the plant version of “respiration”.

Maintenance and Watering

Best time to water is between 5 AM and 10 AM.
Water the root zone but no deeper.
Allowing grass to grow up to 3-inches long will shade soil and reduce evaporation.
Aerating soil helps relieve compaction and allows better water penetration.
Fertilize lawn twice a year.
Change watering patterns as necessary to accommodate new growth.

Sources for More Information

Irrigation Association- provides a wide variety of information and resources related to landscape irrigation (and other types of irrigation).
The Intelligent Use of Water- a white paper by Rainbird discusses the problems which make water conservation necessary and covers ways in which landscape irrigation systems can be designed or adapted help conserve water.
A Homeowner’s Guide to Water Efficient Landscapes- Also a guide by Rainbird but concentrating more on water conservation through irrigation details.
National Resources Conservation Service Water supply forecasts for the U.S., including streamflow, reservoir, surface water, snowpack, precipitation, temperature and information on how to interpret the information.

Peak to Prairie Home Inspection Service

Outdoor Water Conservation