Designing your Irrigation System

If you are looking for information on drip irrigation can be found here.

How Do I Start

You need a design! To do this you need a plan of your property drawn to scale and you need to know your water flow.

The Plan

Use graph paper or a commercial irrigation planning guide and draw to a scale of 1cm = 1m (100:1). Show all gardens, large trees, paths and driveways. Show any retaining walls and fences. Indicate where your water meter and any garden taps are located.

Water flow

Grab the laundry bucket (9litres) and head for the tap at, or nearest to, your water meter. Take all the hose fittings off and turn the tap full on. Shove the bucket underneath and time how long it takes to fill. Simple! Now refer to the chart below and you have your water flow in litres per minute. If you are going to use more than one tap you must do this at each tap.

seconds l/m seconds l/m seconds l/m seconds l/m
3 144 7 62 11 39 18 24
4 108 8 54 12 36 20 21
5 86 9 48 14 31 22 20
6 72 10 43 16 27 24 18

This flow will indicate how many sprinklers you can have on one zone or station. At flows of 18 l/m or less it may not be practical to install a watering system as the number of sprinklers on a zone may be 2 or less.

The Design

The basic design of a watering system can be done on paper but be prepared to make some modifications as you do the installation. First some basic points:

  1. All sprinklers should, where possible, be located on the edge of the lawn spraying in. Spray away from buildings, paths, driveways and gardens.
  2. The dimensions of the lawn determine the radius of sprinkler to be used i.e. 3m x 6m lawn would use 3m radius sprinklers and 10m x 30m lawn, 10m sprinklers.
  3. Sprinklers should be spaced "head to head" i.e. if the radius is 3m then space the sprinklers 3m apart along both long sides of the area. This is required because a sprinkler leaves a dry area under itself. It is rare for a lawn to be exactly the dimensions required so stretching the spacing must be done but remember at least one sprinkler must spray over another.
  4. Break up lawn areas into rectangles and squares to aid in the design process. Odd shaped areas can be a problem, use a compass and draw the radius arcs of each sprinkler modifying the design until coverage is complete.
  5. Make sure you identify each sprinkler by type, arc and radius on the plan to make it easy to link them together into stations or zones.
  6. For reliable performance use large gear drive sprinklers (PGP, RB5000 etc) at 10m radius and medium gear sprinklers (PGM, RB3500 etc) at 7m radiuses. Spray sprinklers list at 3m, 3.7m, 4.5m and 5m.

So now do the design. Have fun!

Neta have developed a useful tool which can help with determining the number and location of irrigation sprinklers. Irrigation Store does not stock the Neta range, but our range of professional large gear drive sprinklers (PGP, RB5000 etc) and medium gear sprinklers (PGM, RB3500 etc) cover equivalent areas. You can Download the Neta Irrigation Designer from their website.

Creating Zones

Now with the design done you will need to connect your sprinklers up together to create zones that don´t use more water than you have available. Remember you must not mix gear sprinklers and spray sprinklers on the same zone. This is because spray sprinklers put four times more water on the ground per minute than gear sprinklers. The amount of water a spray sprinkler uses depends on the arc and radius whilst gear sprinklers use a constant amount of water for the radius regardless of arc setting.

Use the sprinkler specification charts provided and mark each sprinkler with its water usage. Connect sprinklers together in logical groups until water use is within 10% of the available supply. Mark this as zone 1; continue until all sprinklers are grouped.

You should now have a plan and the number of zones you need to run your irrigation system.

Manual Or Automatic

It´s your system and your choice! Think carefully about this matter.

Manual system: A manual is cheaper but has the disadvantage that you must still turn taps on and off every 10 or 20 minutes. The use of a tap timer, mechanical or electronic, with a manual system is not recommended as the flow loss though the timer varies between 25% and 50% depending on brand.

You will need a manifold at one or more taps to turn the system on and off. Don´t forget you may still need a tap on the manifold for a hose. You can purchase pre-built manifolds in brass or PVC or build one from threaded fittings. However leaks can be a problem when using poly threaded fittings.

Automatic system: An automatic system is more expensive but will operate independently, can be set to water at the best time of day, operate when your away, and can be fitted with a rain sensor. Automatic systems save time.

You will need a controller, either indoor or outdoor with the required number of stations (zones), electrically operated taps called solenoids and fittings, a manifold for the solenoids, multi-core cable, environmentally sealed connectors and a box to cover the solenoids.

It is normal when using an automatic system to tap into the water supply at the water meter and then run a mainline in 1" PVC or 32mm metric poly pipe to other areas of the yard.

The Legal Bit

You must check with your local authorities regarding the legal requirements of tapping into the potable water supply for irrigation. Most states and councils will require a licensed plumber to tap into the water supply and require fitment of a backflow prevention device. Be sure to check for local watering restrictions before you run or program your system.

The Other Fittings

You are going to need lots of fittings and LD poly pipe. Have a look at our Buying Guide: What do I need to install lawn sprinklers for more information.

Frequently asked Questions

Why can´t I just put my sprinklers up the middle?

Well you can, but it causes design problems. It can be seen from the diagram below that your choice is to leave scallops of dry grass or throw water outside the lawn areas.

over throw and under throw

Full coverage and no water out side the lawn area is obtained using sprinklers on the edges as shown below.

full coverage with sprinklers

Can I water lawns and gardens on one line?

Yes you can, but it is not a good idea as lawns and gardens require very different amounts of water. One will end up over watered or under watered.

Can I run all my gardens together?

If you have the water flow you can. However you should consider the water requirements of different plants. Breaking the gardens up into logical groups such as annuals, shrubs and native plants will cater for different water needs.

Can I put drippers and sprays on the same zone?

No. Drippers range from 2 to 45 litres per hour and sprays from 35 litres per hour to 16 litres per minute. Uneven watering is the result.

Sprinklers come in different pop-up heights why?

50mm pop-ups require less depth of trench but are only suited to low growing grasses such as couch. On average lawns the blades of grass interfere with the evenness of the water distribution causing random dry patches.

100mm pop-ups allow the grass to grow longer without disrupting the water distribution. The longer grass blades reduce evaporation, which is better for the lawn.

100mm pop-ups are the best choice in almost all cases.

300mm pop-ups are used in specialist applications such as sloped areas and in some gardens.

What size poly pipe should i use?

The size of poly pipe depends on the application, water flow required and the distance it has to run.

13mm poly pipe is great for small gardens that use drippers or micro sprays. The maximum flow through this size is around 30 -35 litres per minute. 13mm is not well suited to pop-up sprinkler applications.

19mm poly pipe may be used in most applications, gardens or pop-up sprinklers. The maximum flow through is around 44-48 litres per minute. When very long runs are involved it may be better to use 25mm poly pipe as the feeder.

25mm poly pipe can be used when a large flow rate is required or distances are greater than average. Maximum flow rate through 25mm is around 55-60 litres per minute.

Is it safe to wire up the controller and solenoids?

Yes. The output voltage from the controller is 24 Volts and is quite safe.

Does the cable need to be in conduit?

No. To make the cable look neat it is usual to conduit up the wall to the controller. The remainder of the cable run may be safely buried in the ground usually in the same trench as the mainline.

How do I wire up the controller?

A simple diagram is shown below. Basically one wire from one side of each solenoid is joined to the common terminal of the controller. The convention is to use the black wire as the common. One of the coloured wires joins the other side of the solenoid to one of the station terminals on the controller.

wiring up a controller

How do I connect the wires together?

You must use a waterproof connector such as the Scotchloc 314 or the 48JOINER. If a waterproof connector is not used over time the joint will degrade and water ingress will corrode the cable. This will result in intermittent or complete failure of the zone.

What is the difference between indoor and outdoor controllers?

Waterproofing! Indoor controllers are not waterproof and are supplied with a plug pack transformer. Outdoor controllers are housed in a lockable waterproof box with an inbuilt transformer. Outdoor controllers are usually more expensive than indoor controllers.

How far can I run the cable?

Up to 200M using 0.5mm econ cable. Doubling the common wire size or using heavier cable can achieve longer distances.

Can I use a tap timer with a manual manifold ?

The best tap timers reduce the flow rate by 25% and the worst by 50%. If you can afford the flow loss in your system then you can, otherwise no. If you are going to use a tap timer you must do your water flow test with it on the tap.

Where can I find more information on irrigation design ?

Our Links page contains links to other useful resources including online videos.