“Purple water may not be fit for your coffee, but it is perfect for proving that even recycled water deserves a proper bill.” – MJ Martin
Water Metering for Purple Water
“Purple water” usually refers to reclaimed or recycled non-potable water delivered through purple pipe systems. The purple colour is used to clearly distinguish this water from potable drinking water and to reduce the risk of cross-connection between systems. In Canada, reclaimed water guidance recognizes purple as a common identification colour for reclaimed water piping, hose bibbs, and related infrastructure.
Why Meter Purple Water?
Purple water should be metered for the same reason potable water is metered: it is a utility service with operational, financial, and conservation value. Even though it is not drinking water, it still has treatment costs, pumping costs, distribution costs, storage requirements, maintenance requirements, and regulatory obligations. Without metering, the utility cannot properly understand demand, losses, peak usage, customer behaviour, or the real value of the reclaimed water program.
Metering purple water also supports water conservation. Reclaimed water is often used for irrigation, parks, golf courses, industrial processes, construction, toilet flushing, and other non-potable applications. These uses can reduce pressure on treated drinking water systems, especially during dry summer months or in water-stressed communities. Purple pipe systems are specifically intended to reuse treated water safely for non-potable purposes while preserving potable water for higher-value domestic and public health needs.
Metering Is Also About Accountability
A reclaimed water program can become politically attractive because it suggests sustainability, resilience, and responsible water stewardship. However, without accurate metering, the program can become difficult to defend. Municipalities need to know how much reclaimed water is being produced, how much is being delivered, how much is being consumed, and whether the system is reducing potable water demand as expected.
Metering also helps establish fair billing. A large irrigation customer using reclaimed water every night should not be treated the same as a small user with occasional demand. Even if the reclaimed water rate is lower than the potable water rate, consumption still needs to be measured to maintain fairness, recover operating costs, and discourage waste.
Technical Considerations
Purple water metering is not always identical to potable water metering. Reclaimed water may have different water quality characteristics, including suspended solids, biological content, chemical residuals, or variable temperature. Meter selection should consider water quality, pipe size, expected flow range, pressure, installation environment, and whether the meter is used for billing, monitoring, or operational control.
Typically, Metercor would recommend an ultrasonic water meter or a mag meter as a minimum solution. A non-mechanical meter is essential to facilitate the higher level of particulate in the flow. A classic mechanical meter cannot tolerate the water borne particulates.
An ultrasonic water meter is a non-intrusive, solid-state device that uses high-frequency sound waves (ultrasound) to measure the velocity of water flowing in a pipe. These meters, including transit-time (for clean water) and Doppler (for dirty/turbid water) types, calculate flow rate without moving parts, offering high accuracy, low maintenance, and wide flow ranges, often using external clamp-on transducers.
A magnetic flow meter, often shortened to mag meter or electromagnetic flow meter, is a highly accurate, obstruction-less volumetric flow meter designed to measure the velocity of electrically conductive liquids, such as water, raw sewage, sludge, acids, or slurries.
It operates based on Faraday’s Law of Electromagnetic Induction, which states that a voltage is induced in a conductor (the conductive liquid) as it moves through a magnetic field.
A back-flow preventer is also required just in case of any potential cross contamination issues.
For many applications, ultrasonic or electromagnetic meters may be attractive because they have no moving parts and can tolerate a broader range of operating conditions. Mechanical meters may still be suitable in some cases, but the utility should carefully evaluate long-term accuracy, fouling risk, maintenance requirements, and the consequences of under-registration.
AMR / AMI and Purple Water
Automated Meter Reading or AMR and Advanced Metering Infrastructure or AMI can add significant value to purple water systems. Hourly or interval data can show irrigation patterns, unauthorized use, unusual continuous flow, seasonal peaks, and potential leaks. In a reclaimed water network, AMR or AMI can also help utilities compare production volume against delivered volume, improving non-revenue water analysis for the non-potable system.
For larger customers, AMR or AMI can support demand management. A municipality could identify excessive night irrigation, detect stuck valves, or use interval data to encourage off-peak consumption. This is especially useful when reclaimed water supply is limited or when storage reservoirs must be balanced against irrigation demand.
Cross-Connection and Public Safety
Purple water metering must also respect the public safety purpose of purple pipe identification. The meter, box, lid, tags, and nearby appurtenances should be clearly marked as non-potable. Some jurisdictions require warning labels, purple identification, separation from potable water infrastructure, sampling ports, and cross-connection controls.
Metro Vancouver’s non-potable water guidance, for example, refers to purple-coloured pipes, sub-metering, sampling ports, commissioning, water quality testing, and cross-connection testing as part of non-potable system design and operation.
Summary
Water metering for purple water turns a sustainability concept into a managed utility system. It supports fair billing, conservation, leak detection, demand planning, operational control, regulatory compliance, and public confidence. If potable water is worth measuring because it is valuable, reclaimed water is worth measuring because it is also valuable. Purple water may not be drinkable, but it still has a cost, a purpose, and a measurable role in the future of municipal water management.
About the Author:
Michael Martin is the Vice President of Technology with Metercor Inc., a Smart Meter, IoT, and Smart City systems integrator based in Canada. He has more than 40 years of experience in systems design for applications that use broadband networks, optical fibre, wireless, and digital communications technologies. He is a business and technology consultant. He was a senior executive consultant for 15 years with IBM, where he worked in the GBS Global Center of Competency for Energy and Utilities and the GTS Global Center of Excellence for Energy and Utilities. He is a founding partner and President of MICAN Communications and before that was President of Comlink Systems Limited and Ensat Broadcast Services, Inc., both divisions of Cygnal Technologies Corporation (CYN: TSX).
Martin served on the Board of Directors for TeraGo Inc (TGO: TSX) and on the Board of Directors for Avante Logixx Inc. (XX: TSX.V). He has served as a Member, SCC ISO-IEC JTC 1/SC-41 – Internet of Things and related technologies, ISO – International Organization for Standardization, and as a member of the NIST SP 500-325 Fog Computing Conceptual Model, National Institute of Standards and Technology. He served on the Board of Governors of the University of Ontario Institute of Technology (UOIT) [now Ontario Tech University] and on the Board of Advisers of five different Colleges in Ontario – Centennial College, Humber College, George Brown College, Durham College, Ryerson Polytechnic University [now Toronto Metropolitan University]. For 16 years he served on the Board of the Society of Motion Picture and Television Engineers (SMPTE), Toronto Section.
He holds three master’s degrees – in business (MBA), communication (MA), and education (MEd). As well, he has three undergraduate diplomas and seven certifications in business, computer programming, internetworking, project management, media, photography, and communication technology. He has completed over 80 next generation MOOC (Massive Open Online Courses) [aka Micro Learning] continuous education programs in a wide variety of topics, including: Economics, Python Programming, Internet of Things, Cloud, Artificial Intelligence and Cognitive systems, Blockchain, Agile, Big Data, Design Thinking, Security, Indigenous Canada awareness, and more.