One Water – Moving Beyond Purple Pipe

The One Water movement is an approach to water use and infrastructure that places value on all water whether rainwater, watershed or ‘waste’ water.  Especially in the continued California drought, H2O is highly valued no matter its source, and we need to shift our paradigm to support our own water-use cycle:  use, then re-use, re-use and re-use!

In the old paradigm, waste water, whether from showers, toilets, laundry or industry, is routed to a sewage treatment plant, cleaned up, then dumped into rivers or oceans.  Big strides came with the use of recycled municipal water, routed through pipe that is colored purple to differentiate that water as non-potable.  In San Luis Obispo and Santa Barbara, purple pipe brings some 200 acre-ft and 800 acre-feet per year respectively, of recycled water to irrigate parks, sports fields and private landscaping.  The City of Palo Alto currently has purple pipe water being used for irrigation and to flush toilets.

Still, building a whole new infrastructure of purple pipe is expensive, and the system is usually very limited in its reach.  The One Water approach asks, why bother with ‘2nd class’ water?  The waste water is already treated to tertiary standards, so if we add one round of ‘polishing’ through sand filtration or mechanical means the water would be potable.  Voila!  No need for new piping, just a ‘new’ source of water.  San Diego has already completed a Water Purification Demonstration Project and is implementing the system on a large scale.

For us, at a project level we continue to focus first on water efficiency with ultra-low-flow plumbing fixtures and high-efficiency irrigation.  We then incorporate on-site recycled water, such as laundry-to-landscape.  If there is municipal purple pipe water available for irrigation or flushing toilets, great.  But when there is no purple pipe, we advocate for a One Water future where all water gets its best use.

For more information, check out the US Water Alliance.