The early plantings in my new productive garden comprised mainly trees (citrus, macadamias, pome), shrubs (currants, blueberries) and larger shrub-like vegies such as tomatoes, capsicums and bushy herbs like parsley and basil. For these plants, off-line adjustable flow drippers have been ideal, allowing maximum versatility so that I can shut down individual drippers as annual plants finish, and turn them on again when I replant. For larger shrubs and trees, I use two or three drippers, and these drippers are also excellent for my large container-grown camellias, citrus, mulberry and maples.
However, these offline drippers are less suitable for smaller vegie crops such as carrots, bok choy, and peas. For these, I used in-line drip irrigation –5mm Miniscape (15cm hole spacing). For long narrow beds with trees and larger shrubs, I use Techline (30cm spacing).
Inline drip irrigation holds grim memories for many of us gardeners because early products quickly became blocked. I had similar misapprehensions until I saw a line of Miniscape stretching far longer than the recommended maximum of 9 metres, half-buried instead of on top of the soil under mulch, without the recommended flush valve or vacuum breaker (although the system was usually disconnected from the tap when switched off), incredibly still performing perfectly many years after installation.
So how to go about installing irrigation?
I have to admit that although I enjoy nearly all garden tasks, installing irrigation is not one of them. It’s expensive, time-consuming, and important to get right… but at least you only need to do it once!
Re overall design, it’s too big a topic for a blog, but there’s plenty of information online from Netafim. Of course, every garden is different; here are two examples that you can adapt: Netafim Vegetables 1 and Netafim Vegetables 2.
Installing irrigation in a large area seems daunting, but below are a few things I did to make the task more manageable, and adaptations that might work in your garden.
1. Break the area into separate sections – plan the lot first, but tackle them one at a time. I have about fifteen separate stations around my garden which water everything, including the pots. I thought about how each section would fit within the overall system, but didn’t try to do it all at once, not least because I wasn’t going to try to plant everything at once!
2. Check your water pressure (I borrowed a plumber friend’s gauge), then choose the highest flow rated techline that pressure will support per station to minimise watering duration.
3. With 19mm polypipe, you can use standard reducing 19mm-13mm tees and ratchet clips to attach techline, instead of the techline fittings. I also used 13mm elbows and tees directly in the techline.
4. Consider replacing all end caps with one way flush valves at the end of all poly lines with offline drippers. These are expensive, but if you’re like me you’ll be too slack to undo endcaps regularly to flush lines properly.
5. Definitely install both automatic flush valves and air release valves (vacuum breakers) on all lines with techline or miniscape. The flush valve operates for a few seconds every time the irrigation begins, so there’s no chance for muck to accumulate. The vacuum breaker is also very important because it prevents dirt being sucked into the pipes through the holes when the solenoid switches off and the water inside the pipe flows to the lowest point, sucking in air as it goes.
6. Install filters for techline and miniscape lines – I’ve been naughty and haven’t yet added these while using mains water, but will before switching to rainwater. You may need to install pressure regulating valves as well.
7. When buying cheap poly fittings like ratchet clips, joiners, goof plugs (definitely get goof plugs!), elbows etc, always buy a few extra. It’s fine to calculate exact numbers for more expensive fittings like valves and filters, but I guarantee that it is much cheaper than several return car trips to the garden centre to buy a single elbow or joiner (I work in a garden centre and see this happen more often than you’d imagine!). Over ten years of accumulating fittings at five to thirty cents a pop, I now have a nicely stocked irrigation toolbox with everything (especially joiners, goof plugs and ratchet clips) at hand for most repairs and alterations. And did I mention goof plugs?
8. If laying a grid or rectangle in a vegie patch, make sure that it’s designed so you can lift the entire section (perhaps held back with a garden stake) while you dig over the patch or add compost. This isn’t necessary for fixed plantings such as berry beds.
9. If a vegie bed is large or very long, break the area into two or more independent areas with valves so that you don’t waste water if one area is fallow.
10. If laying a single Techline down the centre of a very long, narrow bed that will contain randomly spaced or annual plants, consider snaking it, rather than laying it in a straight line. The extra length will allow you to move the line closer to individual plants.
11. Miniscape is extremely flexible, so don’t lock yourself into a ‘grid’ mindset. You can zigzag, snake or loop this line in any configuration to fit any oddly-shaped garden corner, but try to have a manifold at the end or loop it back to the feed line , so valves can be fitted.
12. If your water pressure can handle only one station operating at a time, make sure to draw a plan of watering times of all stations so they don’t overlap, especially if they are on rotational cycles of different numbers of days. In my case, this is important because inline drippers have longer running times than offline ones.
13. Consider a combination of inline and offline drippers – the inline delivers the minimum water requirement, and the offline deliver extra to plants that need it.
14. Controllers and solenoids. Laying many metres of electrical cable to operate solenoids on 15 stations with taps spread over more than 80 metres is completely out of my comfort zone and expertise, and hiring an irrigation installer or electrician would cost a fortune. However, the double sided taps are evenly spaced throughout the length of the garden, so I bought do-it-yourself automatic systems (well, to be correct, mostly they were Do-it-Geoff systems). These systems have run reliably on batteries (further away from the house) or mains power (around the house) for more than a year now, so I’m very happy with them.
At around $180 each they were very expensive, but not when I considered the cost of hiring someone to install a conventional system – labour and materials would, I’m sure, have been several times my total.
However, I bought two dual outlet digital solenoids and these were disastrous. Both failed within a month of installation, and then the replacements themselves failed after a similar time. However, while researching this blog, I found this YouTube video fix ! And YES it works! So no problems with this unit any more.
I have a Pope DigiFlow on the berries and an earlier, cheaper model on the old garden citrus trees. The latter has operated reliably for one year and I trust that the newer one will perform with the same reliability.
This system ensures my entire garden is automatically watered, even all the pots. The only things that need hand-watering are newly planted seeds and seedlings, and the small pots and punnets of things waiting to be planted out. The endemics and natives were planted in late autumn and will continue to manage on natural rainfall alone.
Of course, hand-watering such a large garden simply isn’t possible – I’d end up wetting only the top few millimetres of soil, concentrating the roots there so that my plants would die at the first missed watering. Plus I’d become a slave to the hose, with no time for other garden tasks!
We save our rainwater tanks for a bushfire sprinkler system from mid spring until mid autumn but use rainwater exclusively for the other six months of the year. However, even using drip irrigation exclusively, with approximately 600 square metres under intensive cultivation my water bill will be quite high this summer. Let’s face it, vegetable gardens and food production are NOT ‘water-wise’ activities! And isn’t it pathetic that I still feel slightly defensive about that, even though producing food in my own garden is far more sustainable than importing it from interstate, or buying locally where growers use just as much water?