upgrade pressurised single-zone drip irrigation to measured irrigation
SZ single-zone, MZ multi-zone, GF gravity feed
Before you upgrade to pressurised measured irrigation, you should check that all the drippers in your garden have the same flow rate. This is unlikely to be a problem if you are using regulated (pressure compensating) drippers.
A container with vertical sides is placed at a location in your garden exposed to full sun, and one of the drippers is positioned so that it drips water into the container. A level line is marked on the inside of the container about 3cm below the overflow level.
All that is need is a bucket
A pressure compensating dripper drips water into the bucket
Start watering when the water level is below the level line and the garden needs watering. Stop watering when the water level reaches the level line. Due to evaporation the water level will fall and so the cycle continues indefinitely. The container is called the evaporator. When it is very hot, water evaporates more quickly and your garden will get more water per week. And when it rains the water level rises above the level line and you will start the next watering much later.
By using a container in this way, you can save a lot of water because the number of litres per week emitted by each dripper is controlled by the weather.
The number of litres per week emitted by each dripper is directly proportional to the net evaporation rate.
A bucket and the weather are used to control the irrigation. It is important to realise that an irrigation controller or a timer cannot adjust to changes in the weather. For example, if there is an unexpected heat wave, an irrigation controller will continue to follow its program and ignore the heat wave. If you happen to be on holidays at the time your garden may die. With automated pressurised measured irrigation (see below), the irrigation will respond appropriately to the heat wave while you are on holidays.
Upgrading pressurised single-zone drip irrigation to pressurised measured irrigation
Step 1. Estimate the preferred number of litres per week for each dripper for the hottest month of the year.
Step 2. Estimate the net evaporation in mm for your locality during the hottest month of the year. In Australia, you can use the Measured Irrigation Nozzle Selector Tool which can be downloaded above. Use the pressurised irrigation upgrade worksheet.
Step 3. Before you can choose an appropriate evaporator you need to calculate the required surface area of evaporation using the estimates from Step 1 and Step 2.
surface area in square metres = (number of days in hottest month)
* (litres per week from Step 1
/ (net evaporation from Step 2) / 7
Step 4. Select a suitable evaporator with vertical sides and with the surface area of evaporation as close as possible to the area you have just calculated.
Step 5. Mark a level line on the inside of the evaporator about 3 cm below the overflow level.
Step 6. Install the evaporator in a suitable location exposed to full sun and position a single dripper so that it drips water into the evaporator during the irrigation event.
Step 7. Fill the evaporator with water until the water level is just below the level line and commence irrigating.
Step 8. Stop irrigating when the water level reaches the level line.
Step 9. The water level in the evaporator falls due to evaporation. Start irrigating again when the water level is below the level line and the next irrigation is required. The cycle continues indefinitely.
Additional steps to automate irrigation using a solar panel
Step 10. Install the float switch on the side of the evaporator so that the lever swings up (the irrigation stops automatically when the water level reaches the level line and turns off the switch).
Step 11. Install the solar panel and the solenoid valve.
Step 12. Connect one lead from the float switch to one lead from the solenoid valve. Connect the other lead from the float switch to the Load positive lead from the charge controller. Connect the other lead from the solenoid valve to the Load negative lead from the charge controller.
Step 13. Connect the solar panel and the battery to the charge controller.
with night only option
to simulate night time)
To understand unpowered single-zone gravity feed measured irrigation, it is recommended that you watch the following video.
upgrade pressurised single-zone drip irrigation to solar-powered automated pressurised measured irrigation
After you have upgraded pressurised single-zone drip irrigation to pressurised measured irrigation, the following components are needed to fully automate the irrigation using power from a solar panel.
monocrystalline solar panel 12V 10W
sealed lead acid battery 12V 7.2Ah
charge controller with night only option
solenoid valve 12V DC
10A power relay
The irrigation will start after sunset provided that the float switch is on. The irrigation will stop when the water level has risen and turned off the float switch (or the sun rises).
The charge controller, solenoid valve, float switch and power relay may be purchased from Measured Irrigation:
charge controller with night only option: $55 plus GST
solenoid valve 12V DC: $40 plus GST
float switch: $40 plus GST
10A power relay: $20 plus GST
solenoid valve, charge controller and float switch