Critical Evaluation of Domestic Irrigation Equipment
This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.
Report no. UWRAA 119
The work of the Water Efficient Appliances Committee (WEAP) recognised the need for a study of domestic irrigation equipment. Since approximately half of the potable water supply is used to water gardens in southern Australia WEAP wished to investigate the development of a rating scheme for domestic irrigation equipment analogous to the scheme in operation for plumbing equipment.
Water efficiency in an irrigation system depends on a number of factors. There are two main aspects to efficiency; firstly a water efficient system and secondly efficient operation particularly in terms of scheduling, or the timing and duration of water application events. In general terms the inefficiencies resulting from incorrect operation of systems are more significant than the water losses arising from the installation of faulty or inappropriate equipment. Notwithstanding this any future rating scheme must be developed with the understanding that all aspects must be dealt with in a coordinated way. A rating scheme which is introduced for equipment is likely to be ineffective unless the other aspects of water efficiency are dealt with. Strategies must be developed to ensure good design and installation practices are followed and people understand the basic principles of efficient garden watering.
High standards of system design and installation can be achieved by the support of industry certification schemes for practitioners and by encouraging consumers to use the services of certified professionals.
Existing standards provide guidelines for equipment standards although some modification is necessary for the types of equipment sold to the domestic market. As well as providing for standard methods of classifying and describing equipment the standards provide for a range of test which can be conducted. The tests include;
- Strength tests
- Functional and operational tests
- Durability tests
Standards exist for all equipment types with the exception of controllers and sensors. Such equipment has the potential to make a significant contribution to water efficiency and the development of standards in this area is important for efficient watering.
In this project tests were carried out on a range of equipment including,
- Sprinklers, rotating, impact and gear driven, pop-up and fixed sprays..
- Tap timers
- Porous pipe
The various types of equipment were subjected to the following tests;
- Catch can tests for uniformity of application rate
- Radius of throw
- Area and shape of wetted pattern
- Head loss measurements over a range of flows
- Emission rate for a range of inlet pressures
- Coefficient of variation of product
- Hydrostatic pressure test
- Life testing involving repeated operation.
The majority of the sprinklers and sprayers tested had poor uniformity, the wetted patterns were significantly different from the “advertised” patterns, and the radius of throw varied from sample to sample. The coefficient of variation of the drippers varied from less than 5% to greater than 40%. The discharge rate over a range of inlet indicate that many of the products are extremely inefficient, having discharge rates varying by a factor of three or four.
The hydrostatic pressure tests generally demonstrated that products are constructed to a quality sufficient towithstand the normal range of water pressures which are measured in domestic situations.
As a result of these test a rating scheme is proposed which sets criteria for product to be classified asA, AA, or AAA. The criteria proposed are:
A: Equipment has met criteria detailed in a standard encompassing general quality standards.
AA: Equipment has met standard requirements and can assist in improving water efficiency.
AAA: Equipment has met criteria specified in a standard and will contribute to improving water efficiency.
A strategy is proposed for the introduction of the rating scheme. It is recommended that the rating scheme is developed as part of a co-ordinated campaign, supported by resources and equipment to help people understand the basic principles of efficient home garden watering.