Q. What is Pressure Compensating?

A. Drip systems apply water to plants at very low flow rates. This minimizes 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 drip emitters compensate for uneven terrain, length of supply tube and varying inlet flows. PC drippers facilitate controlled watering, as each drip emitter performs to a preset flow rate (e.g. 1 gallon per hour), allowing water emitted over a length of time to be easily calculated. This ensures more efficient watering, reducing the risk of overwatering or underwatering. A noncompensating drip emitter will have varying output flows at varying inlet pressures. Therefore, the flow will vary along uneven terrain, and each dripper may 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 noncompensating drippers at the bottom will emit more water than those at the top. PC drip emitters will emit the same amount of water all the way down the slope, providing more even watering on uneven terrain. With all that in mind, don't worry too much about PC versus non-PC. Usually the difference in output between a PC and non-PC dripper will be in the 10% to 15% range. Unless your water is VERY expensive or you have a VERY large area to service, the PC versus non-PC issue is moot.