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Irrigation systems

Going.Local
Published on November 15th 2021
irrigation sprinkler system
Many a gardener has gone out for a weekend or weeklong holiday, to return to the shrivelled remains of a once lush plant. It does not take a big leap to consider the many possibilities that a time-controlled irrigation system has to offer. The question is where to start?
Well, let us discuss some rudimentary steps you can take to learn what you need in terms of irrigation.
overhead mister
Misting systems are ideal for cuttings, seedlings and orchids. Image by Alabama Extension CC0 1.0

What do I need?

Before we start discussing what to buy, ask yourself the following few questions:
  • What do I want to irrigate?
    • Is it orchids, my lawn, garden beds, veggie patch, container garden or fruit trees?
  • How often do I want to irrigate?
    • Every day, once a week, when I am on holiday?
  • How many different watering zones do I want?
    • All my plants get watered at the same time.
    • I have two groups that get watered differently.
    • I have more than two groups.
  • Do I get frost?
  • Do I want to connect a rainwater tank to my irrigation?
Seedlings or cuttings may need frequent light misting similar to orchids or tropicals. If your temperatures are high and you have low humidity (ex. Northern Cape or Free State), you might consider drip irrigation that will deliver the water right to the root zone. For garden borders and lawns a larger sprinkler system would be the way to go.
drip irrigation
Image by nate steiner CC0 1.0

Options for irrigation

Ok, let us take a look at the various options on the market. Your standard plug-and-play sprinkler is a hose connected to a spray nozzle. You can switch it on manually or add a timer. Unfortunately, it has a limited range that will have you moving the nozzle around to cover the garden. A comprehensive sprinkler system that covers a garden requires buried water lines or (in a small system) drip tubing along the surface. Think of your answers to the questions above and then consider the following.
Here are some options to choose from:
  • Micro-drip kits for pots
  • One/Two zone controllers
  • Multi-zone systems like Rainbird can be installed by local companies
Note that drip tubing is 15% more effective in water delivery than sprinklers. Most of the world's drip irrigation research has originated in South Africa and Israel, making it an ideal resource to utilise. The reason behind the extensive research is that SA's annual rainfall of 464mm is almost half of the world average (860mm). You can even decrease your water bill by connecting rainwater tanks or boreholes to irrigation systems.

Do it yourself or get someone?

If you plan on a small localised irrigation system for a select number of plants, then it would be cheaper to do it yourself. That said, greenhouses/conservatories and in-ground systems require technical experts.
Why do I need an expert?
  • Pressure problems: Selecting the wrong size tubing or adding too many drip points will affect the water pressure.
  • Air pockets: Laying your lines incorrectly will cause air pockets to accumulate where the terrain changes, affecting water supply and pressure.
  • Burst lines: Cracks and burst lines will cause water to leak and make your bill skyrocket.
  • Electrical supply: Your irrigation system will require an electrical supply that has to conform to building regulations.
It may be necessary to ask a professional if you plan on using greywater or rainwater from a tank. The latter will need a separate pump (with an electrical supply that is insulated and protected from water) to supply water to the sprinkler system. A dual system that relies on both rainwater and standard municipal water is even more complex.
A pile of dirt
Image by Alan Levine on Flickr CC0 1.0

DIY Need to know

It can be very liberating to try to install your own system. There is, however, some safety precautions and general information to consider when working with drinking water and pressure.
Tips:
  • Water pressure: If you are unsure about your water pressure, you can buy an in-line water counter. Most systems rely on 35-40 PSI. You can cause serious problems at 80 PSI.
  • Placement: Water flows downhill and requires pressure to be pumped up a hill. Place the unit at the highest point in the garden to avoid pressure problems.
  • Backflow preventer: You need this to make sure your drinking water does not get contaminated.
  • Timers: Loadshedding resets some timers to factory settings. Having an internal battery or UPS will help in this regard. Some smaller controllers are battery operated.
  • Emitter types: You get three types 1) Pressure compensated (for uneven landscapes differing more than 1.5m 2) Turbulent flow emitters (level landscape) 3) Short path emitters (works on gravity flow). For a comprehensive guideline on emitters see here.
  • Spacing: Leave 45cm between emitters, no less.
  • Freezing: Remember that poly pipe should replace PVC in areas where the ground freezes.
Getting to grips with all aspects of irrigation may seem daunting, but this quick reference should give you an idea of what to consider. Almost all garden centres have technical staff that can assist you in making the right purchases. To learn more regarding water usage and quality, see our series below.

Have any questions? Post them in the comments below or as a question to the Candide community.

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