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Understanding a drip irrigation watering system

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Understanding a drip irrigation watering system

Drip line and poly pipe.Drip line and poly pipe.Traditional watering systems use sprinkler nozzles to distribute water above ground to plants. This can be unreliable as water may be lost to wind and is more vulnerable to loss through evaporation. The effectiveness of a system can also be dramatically reduced by something as simple as foliage being in front of a spray head.


A drip irrigation system uses irrigation pipe that has pressure-regulated drippers embedded in the line at set intervals. These drippers deliver a set number of litres per hour even at lower water pressure. Drip line is usually installed under mulch. It is an accurate way to deliver water exactly where it’s needed and, as it is delivered slowly, penetration into the soil is more reliable and consistent with little or no run-off.


For a small system, all piping and connecters will be 13mm. For a larger system the supply and connection lines may be 19mm, while the drip line will still be 13mm with step-down joiners used to connect. The exact design of a system will vary with your garden’s needs.


Low volume layout.Low volume layout.   High volume layout.High volume layout.


Delivering water only to the base of plants is ideal for a garden with low water demands. This may be in an area with reliable rainfall or heavy soil that retains moisture well. It may involve using a plain poly-pipe return line to finalise the pressure loop.


A higher volume layout delivers water across the planted area. This sort of design is used with plants that have higher water needs or in gardens with more open or sandy soil.

You will notice with both designs that the system does not have any dead ends. They are both loops. The reason for this is to avoid sections of lower pressure in your system. With a loop, the pressure will equalise in the lines and the output will be equal through all drippers.


For a step-by-step guide, see How to install a drip irrigation watering system.


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Getting Established

Re: Understanding a drip irrigation watering system

Thanks @Adam_W , this is quite helpful.

Finding My Feet

Re: Understanding a drip irrigation watering system


Hi Adam,

Thanks for the write-up.

As you suggested a close loop system, but what will be your proposal or work around if i had to do a single line of 60 metres from back of house to front garden ,for the buxus hedges( or is it possible to do a single line without looping back).The drip line is only for the last 30metres of the line for hedges in front.


Bunnings Team Member
Bunnings Team Member

Re: Understanding a drip irrigation watering system

Hi @SamTee,


It's quite common that a single line and no return line are used in backyards. @Adam_W's design would be an ideal layout though and is quite elegant. I believe that you would only experience issues with low pressure at the end of the line if you are running too many drippers for the available flow/pressure of the tap. It's my understanding that once a closed line without drippers fills and pressurizes with water, the PSI at the end of the line will be the same as the beginning, no matter how long it is. The only way I could see you getting a low-pressure zone at the end of the line is if excessive drippers reduce the flow along its length or the irrigation line runs significantly uphill. However, this comes back to the water flow rate at the tap and working out how many drippers the tap can support. As long as you stick within the taps capacity, in my experience, you'll be fine with a single line. The only time I've experienced issues with a single line is when running sprayers. The last ones didn't run at total capacity, which I expected, due to having far too many (10) on a single 13mm line.


You might like to run a 19mm line for the first 30m before dropping it to 13mm for the dripper section or just running 19mm for the whole length. That will make sure there is an adequate flow rate available. There are also adjustable flow drippers that can be used to offset any discrepancy between their flow rates.


How many plants will you need to irrigate?


Hopefully, @Adam_W can confirm whether you'll be fine with a single line system or not.




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Re: Understanding a drip irrigation watering system

Hi @SamTee 
My pleasure & hopefully it's helpful!
So I am assuming that you have 30m of what is really supply-line before you get to the actual drip-line? Or is that first 30m of line feeding other sections too?
Assuming that the first 30m is only supply-line to feed the section of the buxus then that can be a single line as it is effectively becoming an extension of the main pipe.

The loop can then just be around the buxus area.
Drip-line is what they call 'pressure regulated' which basically means each dripper will theoretically deliver the correct volume of water at almost any pressure, high or low, however maintaining that pressure loop design makes sure that there is an even pressure AND volume of water being delivered to the all parts of the line.



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