Garden Irrigation help planning and legal requirements.

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The first thing you must do is plan your irrigation system - you would not go on holiday without first planning it.
  • To begin with, draw up your property accurately, showing as much detail as possible. You must include such things as paths, trees, sandpits, pool, washing line, and garden beds etc. The ideal scale is 1:100 which is 1cm for each metre of your property.
  • Decide if it is to be automatic and where you will put the controller. This is usually in the garage or laundry where you have easy access to either the front or back garden. It is also preferable to keep valves together and the pipe as short as possible. Water pressure must also be taken into account on bigger runs as this will determine the wire gauge. Normal wire is 5mm which is suited to short runs and good pressure.
  • The water source is usually taken from within the property  as close to the meter as possible. This allows for an isolating ball valve and dual check valve.
  • LICENSED PLUMBERS OR IRRIGATION INSTALLERS ARE THE ONLY PEOPLE LEGALLY AUTHORISED  TO CUT INTO THE MAIN LINE. LEGALLY YOU ARE ABLE TO INSTALL AN IRRIGATION SYSTEM FROM  THE SOLENOIDS ONWARDS.
  • It is advisable that your licenced installer puts in a master solenoid. This will come on at the start of a cycle and turn off at the last zone.This master valve will stop a faulty valve running indefinately, wasting valuable water and perhaps burning out a pump if it empties a tank.
  • If you are in a town don't try to run too many sprinklers on a line. Do a bucket test with a nine litre bucket.and a water pressure gauge.
  • Turn the tap on full  and read the pressure. For example, a 90psi  static pressure tells you that you will need a pressure pipe rated above 90psi class .
  • Next we open the stop valve to get a reading of 50 psi. Fill the bucket and at the same time, count how many seconds it takes to fill the bucket. If it takes 15 seconds to fill the bucket, we now multiply the bucket size - most being 9litres- by 60seconds to get a minute which is 540 seconds. Now divide our 15 seconds in to it and  we have 36 litres a minute.
  • Now we need to know how much water we need for our zones if we want to use Rotors for our lawns, and sprays to our garden beds. We know from the sprinkler specifications that a rotor runs from a minium  of 30 psi to50 psi.
  •  We have chosen a sprinkler to do 12 metres and it uses 9 litres a minute We have available 36 litres a minute. Don't assume you can run four Rotors -which is 36 litre- as you must as a rule of thumb take off 20 percent to allow for friction through valves, backflow sprinklers  etc. and when others are watering at the same time. So we have only in round figures 29 litres per minuite, therefore  three sprinklers may be used on a zone of 9 litre a minute Rotors. This is  providing you are using minimum of 25mm low density poly pipe. The same principal applys to sprays -  they work well from 25 psi.
  • Try to limit the amount of water to the following pipe sizes.                                                                     20mm 15 litres max      25mm 30 litres max     32mm 60litres max 
  • Thread tape is not necessary after valves, however on poly pipe always make sure ratchet clips are used. If not used, pipes are sure to blow off. It is best to keep the pressure to below 40 psi in poly systems.
  • For sprinkler systems using a pump, the pipes are generally larger and less zones required. A coarse filter is required at the pump preferably on the discharge side.
  • Finally you can install a rain cut off sensor anywhere it is covenient between the valves and the controller.
  • THE RAIN SENSOR IS A COMPULSARY COMPONENT OF AN IRRIGATION SYSTEM IN VICTORIA - CHECK WITH THE WATER AUTHORITY IN OTHER STATES.
I hope this gives you a better understanding of a watering system and answers some of your questions before you purchase anything.










                                             
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