What is Pressure Compensating?

Drip systems apply water to plants at very low flow rates. This minimises evaporation losses and limits the water to the root zone of the plant by “Putting water where it counts!®".

 

Pressure Compensating, or PC, is a term used to describe an emitter that maintains the same output at varying water inlet pressures. Therefore PC drippers compensate for uneven terrain, length of supply tube and varying inlet flows. PC drippers facilitate controlled watering, as each dripper performs to a pre-set flow rate (eg 4 litres per hour), allowing water emitted over a length of time to be easily calculated. This ensures more efficient watering, reducing the risk of over-watering or under-watering.

 

A non-compensating dripper will have varying output flow at varying inlet pressures. Therefore the flow will vary along uneven terrain, and each dripper will emit a different amount of water depending on its location on the supply line. The pressure to a drip emitter can vary due to the slope of the land and the length of the supply tube. If an irrigation system is installed down a slope, there will be higher water pressure at the bottom of the slope than at the top, and non-compensating drippers at the bottom will emit more water than those at the top. PC drippers will emit the same amount of water all the way down the slope, providing more even watering on uneven terrain.


 
Non-compensating emitters on uneven terrain


 
Pressure Compensating emitters on uneven terrian

 

The optimum pressure for drip emitters is 100 kPa to 350 kPa. Where supply pressure is higher than 350 kPa, a pressure regulating device should be installed at the start of the irrigation system.