Pressure Regulation and Saving Water

Today I read about another manufacturer receiving the EPA WaterSense certification for their pressure regulating spray bodies.  This tells the end user that installing these spray heads POTENTIALLY would reduce an irrigation system's total water use, when compared to using spray heads without any pressure regulation.

POTENTIALLY is annoyingly capitalized to stress that the simple use of pressure regulating spray heads does not always result in saving water.  All spray and rotary nozzles have an optimal operating pressure.  At this pressure they have the greatest potential to operate, as designed, in a real world setting.  What this means is that it is emitting beautiful water droplets, and if there is head-to-head coverage, we have a near uniform amount of water be distributed across an area.  (Quick disclaimer:  This is not usually something that is easily visually observed.  A sprinkler can look beautiful and have terrible uniformity.)

Pressure regulating spray heads help with obtaining this optimal operating pressure WHEN OPTIMAL PRESSURE IS EXCEEDED.  If we look closer at manufacturer specifications, we find that these products typically require a pressure differential of 10 psi.  Most manufacturers offer these products in a 30 PSI model, meaning we would want at least 40 psi at the base off all the heads.  If we are analyzing a system that has around 32 psi at the base of a head, then we would no longer be at optimal operating pressure for the nozzle.  We would be below optimal pressure, which could result in using more water than if we did not use the pressure regulating spray head.

This explanation is not to demonize the WaterSense certification.  I am personally a supporter of WaterSense.  I feel it is doing a lot of good things for our industry.  However, I feel it is important that we, as industry professionals, recognize that there is no silver bullet for water savings.  We need to understand how things work, so we are able to provide the end user with the best possible solution.  Sometimes this may mean, that we recognize what we do not know, so we can enlist someone to aid us in our sustainability endeavours.