The Unpowered Terracotta Valve is suitable for automatic sprinkler irrigation or drip irrigation. The valve operates with water supply pressure in the range 10 kPa to 800 kPa. The interval between irrigation events is automatically controlled by the on-site prevailing weather conditions (namely, evaporation and rainfall).


Terracotta is porous and so the water level in the pot falls as water seeps through the pot. A float inside the pot floats on the water. When the water level reaches the low level, a magnet inside the float activates the valve so that the valve opens and the irrigation starts. During the irrigation event a control dripper drips water into the pot and the water level rises. When the water level reaches the high level, the magnet inside the float disengages from the valve so that the valve closes and the irrigation stops.


For above ground installation, position the Unpowered Terracotta Valve in a suitable location in your garden so that the evaporation matches the evaporation at your plants.


For in ground installation, position the Unpowered Terracotta Valve in the hole between two plants so that rim of the pot is above ground level. Back fill soil around the pot. Because the terracotta pot is in the ground near the roots of plants, the Unpowered Terracotta Valve responds to changes in plant transpiration. As the crop grows and requires more water, the irrigation frequency increases automatically.


During an irrigation event, the control dripper replaces the water that has evaporated since the previous irrigation event. This volume is called the control volume. The Unpowered Terrcotta Valve has a control volume between 77 ml and 333 ml. 


Key features

  • Unpowered (no batteries, no solar panels, no electronics, no computers, and no WiFi)
  • Water supply pressure 10 kPa to 800 kPa
  • Half inch inlet and outlet
  • Use for sprinkler irrigation or drip irrigation
  • Use for gravity feed or pressurised irrigation
  • Adjust the water usage rate by adjusting the control dripper
  • Adjust the interval between irrigation events by adjusting the float
  • Adjusting the water usage rate does not affect the interval between irrigation events, and adjusting the interval between irrigation events does not affect the water usage rate
  • Responds automatically to on-site evaporation and rainfall
  • The irrigation frequency increases significantly during a heat wave
  • Install above ground or in ground
  • Provided the same drippers are used throughout the irrigation application (including the control dripper), the dripper discharge is independent of the water supply pressure
  • Irrigate directly from a rainwater tank without using a pump
  • Water in the terracotta pot is protected from debris, algae, mosquitoes and thirsty animals
  • Simple, unpowered, and low tech, and therefore fewer things can go wrong
  • Leave your irrigation application unattended for months on end

Unpowered Terracotta Valve