Product Certification Standards for Sensors and Other Water Quality Test Devices

Protocol 524: Water Quality Testing Devices for Drinking Water (P524) is the first product certification protocol to provide manufacturers of water quality test devices (WQTDs) with third-party verification of the accuracy and precision they claim in marketing their products.

This testing protocol covers any device, sensor or test kit used to measure water quality parameters in drinking water, including benchtop-style devices that analyze discrete aliquots of water, and in-line devices that give readings on continuously sampled/measured water in real time or after a short wait period and where operation of the WQTD does not require access to laboratory facilities or equipment.

Under the protocol, the WQTD is evaluated at the low, mid, and high points of the operating range for the measured parameter(s). The readings from the device are then compared to a lab reference method for the same parameter. This comparison is used to calculate the accuracy and precision of the WQTD for each parameter, which is then compared to the manufacturer’s published claims. WQTDs that meet or surpass the manufacturer’s claims may be listed and certified to P524 and are entitled to bear the NSF P524 certification mark.

This protocol joins two well-established water standards, NSF 61 and NSF 50:

NSF/ANSI/CAN 61: Drinking Water System Components- Health Effects (NSF 61)

WQTDs that contact water in the drinking water transmission system, such as in-line sensors, are also covered under NSF 61. This standard addresses the health effects of chemical contaminants and impurities that may be leached from the device. Products tested to the standard are exposed to formulated test waters over a defined sequence of days, and the resulting leachate water is analyzed and evaluated for any contaminants that may have leached from the product. Products may only be certified to NSF 61 if no individual contaminant exceeds the health-based criteria as established under the reference standard NSF/ANSI/CAN 600.

As most U.S. states and Canadian territories/provinces require certification to NSF 61 for drinking water system components, certification to this standard is a prerequisite for applicable products to be certified to P524. (Both certifications may be pursued concurrently.) WQTDs that do not contact finished drinking water, such as benchtop units that analyze discrete samples of water, do not require certification to NSF 61 in order to be certified to P524.

NSF/ANSI/CAN 50: Equipment and Chemicals for Swimming Pools, Spas, Hot Tubs, and Other Recreational Water Facilities (NSF 50)

This standard addresses the accuracy, precision and other performance characteristics of WQTDs used to monitor and measure recreational water quality parameters to help maintain optimal water quality in swimming pools, spas, and other recreational waters. Testing — performed using synthetic pool water — evaluates accuracy across the product’s operating range, as well as precision, reproducibility and shelf life. WQTDs that measure a given parameter in both recreational water and in drinking water systems may be eligible for certification to NSF 50 in addition to P524.

Water utilities, regulators and pool operators know and recognize the NSF mark and the level of quality it represents. Certification to P524, NSF 61 and NSF 50 provide multiple ways to demonstrate the quality of a WQTD for use in drinking water, recreational water, or both.