Your garden has unique watering needs due to your soil type, plants and climate.
Knowing your flow rate is step 1 to choosing the right reticulation system.
Here we teach you how to calculate flow rate f; the easy way.
You'll learn about flow Vs. pressure, why it matters and the DIY bucket test method. (Flow rate calculator included!)
Let's get started!
What is Flow Rate?
Flow rate is the measurement of the amount of fluid passing by a location in one area over time.
In this instance, flow rate is the amount of water passing through a given point over a period of time.
An accurate flow rate measurement ensures water-control processes run smoothly, safely and cost effectively.
You must know your flow rate in order to determine which irrigation system is best for you.
Why Does it Matter for Your Reticulation System?
Knowing your flow rate will help you optimise your irrigation systems' overall effectiveness.
It forms the basis of your irrigation set up, whether you're using drip lines, sprinklers or any other type of system.
Determining your flow rate will help you:
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Choose the best irrigation system for your needs
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Choose the correct pressure regulator
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Choose the correct size pump, sprinklers and nozzles
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Maximise efficiency of your system's watering schedule
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Keep water usage costs to a minimum
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Not to exceed permitted municipality water usage limits
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Figure out if there's a blockage in the pipeline or a problem with the water supply
What are the Flow Rates Required for an Irrigation System?
A typical flow rate for mains water would be around 40 - 60 LPM depending on your location.
Drip systems usually require less flow rate compared to other systems such as popup and gear driven sprinklers.
The exact flow rate you need will depend on your property's unique needs, the soil type, the plants or crops you're growing, and the climate conditions.
Understanding Flow and Pressure
Where 'flow' is the amount of water moving through an area over time, 'pressure' is the force at which that water is moving.
Flow and pressure are different concepts, and one is not indicative of the other. Both flow and pressure need to be determined in order to install an irrigation system.
In fact, a 5% change in pressure can result in a 10% change in water flow rate.
Pressure is what propels the water through the pipes. It is measured in PSI (pounds per square inch), KPA (Kilopascals) or BAR. To measure static water pressure (pressure reading with no water passing through) you will need a flow testing device with a gate valve and pressure gauge. Attach this directly to the tap at your main water supply and turn the tap on full flow to get a reading.
Irrigation systems, namely the sprinkler outlets used, will have an optimum operating pressure rating. For example, the Hunter Pro-Spray Popup Sprinkler has an operating range of 100- 700 kpa but when installed using a 10 foot Hunter Fixed Arc Nozzle this is refined down to 210 KPA or 2.1 BAR. The precipitation rate for this sprinkler combo is 6.38 LPM which will vary depending on the amount of pressure at the sprinkler head.
See this video for a guide to measuring flow rate.
By balancing flow and pressure you will get the most out of your irrigation system by ensuring:
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Even watering over the whole garden
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Minimal water wastage
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Plants receive the nutrients they need to be healthy
High pressure can result in misting. Likewise, low flow can result in dry spots. Ensure you measure flow and pressure accurately and adjust your irrigation system to suit.
The Bucket Test
Use this handy DIY method to calculate your flow rate yourself.
You will need:
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a bucket (any size: note the litre capacity)
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a timer or stopwatch
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a garden tap
The Bucket Test Method:
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Remove any fittings from the tap
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Open the tap fully
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Place bucket underneath the fully open tap and immediately begin the timer
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Once the bucket is full, stop timer
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Complete the flow rate equation using the following formula: 60 divided by (the time it takes to fill the bucket) X (the bucket size in litres). The answer is your Litres Per Minute (LPM) result.
For example: 60 divided by 17 seconds X 9 litres = 31.8LPM
To allow for pressure loss, deduct 20% of the total: 31.8 - 20% = 25.4LPM
If you use a flow tester, you do not need to deduct 20%.
See the bucket test in action here.
Flow Rate Bucket Test Calculator
Summary
Understanding your water pressure and maximum flow rate will enable you to choose the right equipment for your irrigation system factoring in sprinkler, nozzle and pump sizing.
The easiest way to test your water flow rate: using the bucket method! No complex equipment required. Simply use our bucket test calculator to determine your flow rate as described above. For a more accurate reading (recommended) grab a flow tester tool from your local Nutrien Water store and do the same measurement at 100 KPA pressure intervals. This will give you the best indication as to what sprinklers to use and how many can go on a single station.
Need help with your design?
Once you've used our flow rate calculator, submit your information here for a free irrigation design and quote.
