Last Updated Dec 3, 2010 · Written by Craig Gibson
Irrigation & Drainage
Drip irrigation is the most water efficient system available to water your garden. Some systems are so efficient that they only allow a few litres of water per hour to fall into the soil! We’ve put together a guide on what you need to know about drip irrigation.
Overview of Drip Irrigation
Drip irrigation is the best way to water the plants at ground level where they need it the most. It was initially developed for the agricultural industry but it is now extremely popular in Australian residential gardens, due to their water efficiency. You can set up a system that waters the entire garden at once, or you can set up a system that irrigates certain parts of the garden as efficiently as possible. For example, you could have a separate system for vegetables, natives, and other plants as they all have different water requirements.
Advantages of a Drip Irrigation System
- minimised fertiliser or nutrient loss due to localised application of water
- highly efficient water distribution
- allows recycled water to be used safely
- maintains water within the plant’s root zone where it is most needed
- reduces soil erosion
- supply can be regulated by controlling the output of valves and nozzles
- piping is easily laid and suitable for most environments
- great for windy areas
- suits all types of soil and plants
- reduces the risk of plant fungal and insect problems
- loses the least amount of water from wind, evaporation and run off
- doesn’t waste water on weeds
Disadvantages of a Drip Irrigation System
- system may cost more to install initially than other irrigation types
- the sun may affect the lifespan of the tubes used in the system
- the system may clog if not properly filtered and maintained
Components of a Drip Irrigation System
The components of a drip irrigation system include:
- Integrated drip line – this could be piping or tubing and it’s usually made from PVC and varies in diameter, depending on the water pressure needed. The line can be laid above or below ground, or in a layer of mulch.
- Drip emitters – these attach to the standard PVC irrigation piping and apply a consistent amount of water to the plants. Generally speaking, the cheaper emitters have a highly variable flow rate that depend on water supply pressure while more sophisticated, commercial quality emitters have pressure compensating systems to ensure that water flow is constant.
- Weeping hoses – are normally made from black recycled tyre rubber and can be attached to a fixed watering system or an ordinary garden hose. They can be laid in the same way as integrated drip lines.
- Controllers – these manage the flow of water through the irrigation system. Simple controllers such as a mechanical tap timer only need to you set the watering time required. More complex controllers are capable of watering different garden zones at different times and even on different days.
- Backflow prevention device – backflow occurs when there is reverse pressure in the water supply system, drawing contaminants such as fertiliser back into the drinking water supply. The backflow prevention device stops this from happening and prevents illness that could occur as a result of contaminated water.
- Rain switches – these turn the irrigation system off during wet weather, stopping you from over watering the garden. Rain switches can be connected to most electronic automatic controllers.
- Soil moisture sensors – these are placed beneath the soil at a specified depth to measure the amount of moisture in the soil. When the level drops below a predetermined level, it allows the irrigation controller to operate, thus watering the garden. These can be fitted to most electronic automatic controllers.
- Joints and connectors – t-joints, elbows, couplers, and end caps connect the piping in your irrigation system.
- Filters – these are essential as emitters have small openings that are easily clogged. Use a 150 mesh screen or one with a higher mesh number.
The Importance of Filters
Nearly all drip irrigation systems will require a filter. This is especially important if you are running your pipes from your rainwater tank. Filters prevent clogging of the system by small waterborne particles. Some residential systems will be installed without filters as the water supply is already filtered at the water treatment plant, but all drip irrigation manufacturers recommend that filters are used and generally will not honour warranties if there is no filter.
Designing and Installing Drip Irrigation
Design is an important part of any drip irrigation installation. It is a good idea to work out the number of connectors needed for the system. Be aware of your plants’ watering needs – plants in sunny areas need more water than plants in shady areas. Pay attention to the slopes and the type of soil in your garden. If you have a heavy clay soil, you may require more water pressure to compensate. Select the drip emitters to match your plants’ watering requirements and consider where joints and connectors are best placed. Before digging any trenches, lay the piping above ground. This will allow you to see if you have the best placement first, before any heavy work.
When digging, be aware of the placement of utilities such as drainpipes, electricity cables, gas, etc. A trench 10cm deep should be more than adequate unless you have sandy soil, in which case it should be a little deeper. It is a good idea to have your drip emitters above the ground, to minimise the chances of them becoming clogged by dirt.