Ask any gardener about how to have the perfect garden and they’ll wax lyrical about the right plants in the right place, good maintenance, fertilising and keeping on top of pests and diseases.
Funnily enough, most don’t mention one of the foundation stones of a great garden, and that is using correct watering practices.
While watering with a hose by hand can be a wonderfully therapeutic exercise, it’s not the wisest way to get the job done, as distribution is uneven and the water often doesn’t soak down deep enough to where it’s needed.
Hosing can actually cause all kinds of problems, as the plants start to develop more surface roots seeking the water and are then more prone to heat stress in hot weather.
You can also lose lots of water to evaporation if it’s applied to warm soil or mulch. And in the case of sprinkler-style irrigation systems, they often scatter water to the four winds.
So what’s the best solution for watering the way your plants need it without wastage? Install a drip-line watering system DIY.
How a drip line works
A typical irrigation system uses black poly pipe into which you plug various sprinkler heads and nozzles.
Drip line looks different, as it’s brown or purple and has small holes every 300mm along the tube.
Inside the pipe, behind each hole, is a tiny regulated dripper that releases a set volume of water an hour.
This slow watering allows for greater penetration deep into the soil, reducing runoff and evaporation.
As drip line has a set output, which is found on the sticker, it’s easy to calculate water usage and the capacity of your tap to run a system. You can then work out the maximum length of drip line you can install.
To determine the flow rate of the tap for the irrigation system, run it at a normal rate into a 10L bucket and time how long it takes to fill.
So if it fills in 30 seconds that is 20L a minute or 1200L an hour (2 x 10 = 20, 20 x 60 = 1200). The line we used puts out 1.6L an hour per dripper, with a dripper every 300mm.
To find the number of drippers the tap can feed, divide the flow rate by the drip rate (1200 ÷ 1.6 = 750). This means the tap can feed 750 drippers.
Calculate how much drip line you can install by multiplying the total number of drippers by the interval between them in metres (750 x 0.3 = 225).
In theory, this tap could supply 225m of drip line, but it’s better to stick to a length that is 50% of your tap’s full capacity, or less.
The recommended length may also vary with the drip line, so check the manufacturer’s instructions.
TIP If using grey or recycled water, or harvested non-potable tank water, make sure you use the correct colour coded purple or mauve pipe.
A drip line tube has small holes that appear every 300mm
Install a drip-line system
Clear mulch or soil from garden beds to make a trench, using a hoe to remove enough so the system can be concealed once laid. Drip line should be positioned around the most active root zone of plants, which is just in from the edge of the foliage canopy.
Lay the drip line in the trenches, cutting it to length as you go. Ensure the line is cut square and sitting flush to end fittings, securing the joints with pipe clamps. Use drip line around plants and connect it with poly pipe in the places where water isn’t needed.
Avoid dead ends by bringing all pipes back to the main line, creating a pressure loop for consistent water pressure and equal output from each dripper. Use pins to anchor the pipes. TIP To loop the system, run poly pipe back to the start and use T-joiners.
At the furthermost or lowest end of the irrigation system, add an in-line tap. Connect the system and run it
for a few minutes with the tap open to clear any debris from the lines. You can also do this every few months for general maintenance.
Once the irrigation system is fully installed, connect and program a tap timer, adding a tap splitter so a hose can be connected to the other side. TIP Add a check valve, or backflow prevention device, to stop water flowing into the mains supply.