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Unpowered  Evaporative Valve

It is recommended that you watch the YouTube video Unpowered Measured Irrigation Controller


Unpowered Measured Irrigation Controller showing the adjustable float and the adjustable control dripper 


It is assumed that the smallholder is using drip irrigation (either pressurised or gravity feed) on a garden or a small plot of land. Using the Unpowered Measured Irrigation Controller, you can upgrade your drip irrigation system so that all your plants are irrigated automatically. You can leave your garden unattended for weeks. This will allow you to become involved in other activities away from the garden; for example, travelling to the market to sell your produce.

The Unpowered Measured Irrigation Controller does not need any electricity. Furthermore, it is a smart controller because the water usage rate is controlled by the prevailing weather conditions. In fact, the water usage rate (litres per week for example) is directly proportional to the net evaporation rate (that is, evaporation minus rainfall).


You can adjust the water usage rate by adjusting the control dripper. You can adjust the irrigation frequency by adjusting the float.


Adjust the water usage rate (litres per week) by adjusting the control dripper


Adjust the irrigation frequency by adjusting the float


Cylindrical float and seven float rings are provided

In September 2019, the Unpowered Evaporative Valve was accepted by the Expert Panel for theSmart Approved WaterMark.

The Unpowered Evaporative Valve can be purchased online from the Measured Irrigation Shop.

  • Can be used for pressures 10 kPa to 800 kPa.

  • Unpowered (no batteries, no solar panels, no computers, and no electronics)

  • Can be used for drip irrigation or sprinkler irrigation.

  • Can be used with pressure compensating or non pressure compensating drippers.

  • Uses much less water without affecting the yield

  • Simple, low tech and easy to assemble and therefore fewer things can go wrong

  • You can leave your irrigation application unattended for weeks on end

  • Detailed instructions are in the Unpowered Evaporative Valve User Manual.

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