Irrigation Equipment: Facts to Consider

Posted on September 20, 2017


TIPS

  • Contract a professional irrigation designer; insist on a system to suit your plants and your soil.
  • Install efficient micro-irrigation emitters wherever possible. 
  • Install an irrigation controller with multiple programs, seasonal adjustment, and a rain switch. Consider soil moisture devices.
  • Mulch around your plants to conserve water in the soil. 
  • Irrigate to encourage deep roots - but don’t over-irrigate. 
  • Monitor your water use – you may need expert advice. 
  • Check and clean the various components of your system at the beginning and end of the irrigation season to make sure they are working properly.

Filtration

It is easier to clean a single filter than many emitters. An effective filter which protects downstream components, is an important feature of all irrigation systems.

Four types of filters are used to protect irrigation systems:

Screen filters – typically used for relatively clean water (e.g. city water) but not recommended where organics such as algae are present. They usually comprise of a plastic or stainless steel screen and should be manually cleaned on a regular basis according to the degree of clogging that has occurred.

Disc filters – these are made up of plastic discs, stacked on top of one another in the filter housing. The discs are grooved according to the rating of the filter. The grooves become gradually blocked over time with the contaminants in the water. Manual cleaning involves loosening the disc cartridge and washing the discs individually. 

Sand media filters – these filters are pressurised tanks containing sand and are primarily used where organic matter content of the water is high. The dimensions of the sand grains are chosen according to the size of the emitter orifice they are intended to protect. 

Sand separators – strictly speaking, these are not filters, but are devices that cause the water to be rotated in the body of the equipment. Centrifugal action forces heavier particles within the water to move to the outside of the stream and then fall to the base of the separator where they are collected and can be removed.

In summary, screen and disc filters are commonly used to protect drippers, jets, sprayers and mini-sprinklers irrigating residential gardens, and all four filter types are used in large-scale agricultural and commercial irrigation projects.

When specifying filtration requirements, it is necessary to refer to the minimum cross section dimensions of drippers and the minimum nozzle size of jets, sprayers and mini sprinklers. The degree of filtration provided by a filter is described either in terms of the size of the holes in the screen in microns, or the number of holes per linear inch. The conversions given below are approximate.

Drip irrigation

Although variable, the dimensions of the smallest pathways in drip emitters are unlikely to be less than (0.6mm) 0.024”. If organic matter is present in the water at high levels, such an emitter will require protection by a 75 micron / 200 mesh filter. If there is only inorganic matter present, a 175 micron / 80 mesh screen will be adequate.

Jets and sprayers 

Minimum orifice size is generally not less than (0.8mm) 0.032”, in which case a filter with a 100 micron / 150 mesh screen will cope with an organic load in the water. A 250 micron / 60 mesh screen will be adequate if only inorganic material is present.

Mini sprinklers 

With minimum orifice size around (1.5mm) 0.06”, filter screen size can vary from 175 micron / 80 mesh (organic matter present) to 500 micron / 35 mesh (only inorganic matter present)

If you are uncertain about the quality of your water supply, or the minimum orifice size of your chosen emitter, seek professional advice.