The impact of long-term drought in Australia means we need to be thinking about better ways to get water to our gardens with the least amount of waste and fuss. With sprayers, sprinklers and hoses, there is inevitably a fair bit of water that goes on paths and surrounding areas, which not only wastes water but also encourages weeds. To get water directly to plants’ roots, drip irrigation is one of the most efficient and focused forms of irrigation.
Drip lines, also known as drippers, dripline and drip tube, have come a long way in the past few years. The most popular and easy to find at major gardening and hardware retailers are extruded, ‘self-cleaning’ inline drip emitters, or ‘drip irrigation tube’. This (generally) 13 mm polypipe has three litres/hour emitters built into the inside of the pipe. Irrigation is an investment in time and money to set up, but you save a lot of water.
The benefits of using a drip irrigation system over overhead sprinklers or hand-watering are fourfold:
- Water is not wasted. Emitters drip onto the soil and water seeps down directly to the root zone of the plants. Plants get water but any weeds next door, don’t. On a windy day, you can water without losing this precious resource to overspray or evaporation. The emitters use three litres/hour, so you can calculate your water needs.
- Time is gained. Hand-watering can take hours each week depending on the size of the garden. It is good observation time; time to check for weeds, growth, pests, etc, but it can be a drain on other activities. Turning on a tap with a timer running is a better option.
- Plants benefit. Particularly, plants susceptible to fungal problems benefit. Sprinklers and handwatering douses not only the soil but also the plants themselves, which can lead to humidity and prime conditions for powdery mildew and other problems.
- They’re easy to install, remove and store. Perfect for renters who may be moving every few years. There are, however, a few drawbacks, although they have remedies too.
- Unlike sprinklers and hand watering, there are a lot of components involved: lines, connectors, clamps that can break and need replacing from time to time. Mulching over the drip lines can help protect them from the sun.
- With the emitters only every 300 mm, in the peak of summer there can be dry patches in vegetable beds. Using more lines across a bed can help mitigate this. For example, three lines across a 600 mm wide bed will allow good water coverage for the entire soil mass.
- Emitters can become blocked by soil or algae that grows in the lines. This may be more prevalent when using unfiltered water supplies.
- Connectors can work loose during hot weather or due to UV degradation, with water flooding your garden.
These ‘blowouts’ at the connectors either between the driplines or driplines and hoses can be caused by pushing too much pressure through the driplines. Driplines are designed to work well at low pressure, so if you are on mains water, you only need about a quarter turn of the tap to apply enough pressure for your system to run well. This can be changed by how big your system is, but an average garden system is not going to need much pressure at all. It can be a good idea to monitor the system to see if there are any blowouts:
- when it’s first installed
- after very hot or cold weather
- if the system has been moved or parts have been replaced
- when getting accustomed to the correct water pressure
Clockwise from top left: A tee connector inserted into the hose ready for the 13 mm polypipe to come off it; A manual timer with four-way splitter with inline filters below; The end of the drip line, tied off and pegged; Sliding the hose onto the connector; A T-shape intersection with plant on dripper hole.
You will need:
- 13 mm polypipe dripline (work out length from your design)
- Tee connectors, elbow joins, four-way connectors and end-stoppers
- A sharp knife to cut the pipe
- A chopping board or piece of wood
- Hot water for heating ends of pipe.
Remove any mulch before installing dripline, to help level out the garden bed and so water from the emitter can penetrate straight into the soil. Replace the mulch after installation to help protect your plants, soil and driplines from the sun.
When setting up a drip irrigation system on new garden beds, make sure to add the pre-planting compost, manure, worm castings and amendments you want to; it’s much harder to turn in compost when drip lines are already installed.
- Before you start, draw up a design of your irrigation system so you know how much pipe you will need and how many T-shapes, elbows and four-way connectors you will need to hold it all together. We recommended three lines of drip irrigation down a 600 mm wide bed. The irrigation pipe comes in various lengths, usually 50 m, 100 m and 200 m. The pipe can run straight or round in circles.
- The best way to install a new system is bit by bit, cutting connecting hoses to size as the system is put together. Start with the first hose connection from the tap. You will need one length of hose that runs along the garden that the drip irrigation line will run off. Allow for enough slack so the hose can run along the ground and doesn’t put any strain on the tap connection.
- Mark the points of the connections for each garden bed on the hose (where you will make cuts and install the connectors). Allow in your measurement for the slight width the connectors contribute to measurements (about 15 mm).
- Make cuts in the hose where the connectors will insert and the drip lines will connect. A standard sharp kitchen knife, serrated or not, works well for this task. Cut the hose on a hard surface, such as a plank of wood or an old chopping board, so the cut is easier and the risk of cutting fingers is lessened. Avoid cutting on soil, as soil may enter the hose and potentially lead to blockages. Make sure you buy the right size connectors to match the hose size and polypipe.
- Install the connector into the hose. It can be difficult to push connectors into hoses and dripline. To make this easier fill a thermos with boiling water. Take this out into the garden and dip the end of the hose or drip line into the hot water for 10 seconds. This will expand the hose or dripline enough to push the connectors in with ease.
- Measure the length of the pipe you will need for the length of your bed. Rolling out dripline can be tricky as the line is coiled and holds the shape for some time after. Hooking the line over something to stretch it and measure accurately is one option. Using a flexible measuring tape to measure the pipe is another method. Or find an extra person to help with this step. Another more rudimentary way is to estimate the length of the dripline that is needed on the bed.
- Once the lengths of dripline are cut, secure the hose and dripline to the connector with 13mm clamps. These can be metal or plastic. The clamps can help ensure the lines or hoses don’t pop off the connectors under pressure, or after a hot day.
- After two or three lengths of driplines have been connected and secured to the connectors and hose, give them a brief flush out before securing the ends (step nine). Connect the irrigation system to the water source and run the water for 30 seconds or so. This makes sure there is no soil, debris or spider nests in driplines. This is an especially good thing to do after the driplines have been stored for any length of time. Repeat as you attach each group of two or three driplines. If you are connecting to a dam or a pond where the water is likely to have algae or other debris, it is important to install a filter before the dripline, so debris doesn’t block the system.
- Stretch the dripline along the length of the bed. Either place an end piece in the line, connect it to the other lines with elbow joins and tee-joins or bend the last 200 mm of the line back on itself hard, so water can’t seep through. Tie the bent line with strips of material, bailing twine or strips of rubber innertube from old bike tyres.
- When the system is finished, test and observe if there are any leaks, weak spots or changes to the lines when water is pushed through the system. It’s good to attach a timer to the hose, so you can set it for the length of time you want to water. You can either attach a simple twist timer that you set when you turn on the tap, or you can have a more complex system that you can set to turn on and off whenever you want your garden watered.
It will cost $100–200, depending on the system you set up but it is definitely worth it for the water you save. You will also be more likely to have plants that thrive as watering will be easier and you know the water will get directly to your plants.