By Rick Andrew

Modern cars have a multitude of monitoring sensors and alarm systems to help drivers avoid potential inconveniences or even dangerous situations—and stay on track with required maintenance. It’s very unlikely I’ll ever run out of gas, even if I fail to check my fuel gauge regularly, because my car has a monitoring sensor and alarm that flashes and sounds if my car starts to run low. Similarly, it’s easy for me to stay on schedule for changing the oil, because my car tracks my oil change and engine usage history for me, and lets me know when the car is due for an oil change. Because of these sensing and monitoring devices, I have a much lower chance of being stranded in the middle of nowhere at an inopportune time because of a car problem that occurs from hidden mechanical wear or damage. The sensors and alarms on my car keep me safer, especially if I’m the type of driver who fails to keep careful track of maintenance or inspect the car regularly.

Sensing and monitoring devices are also being incorporated into many of today’s modern residential drinking water treatment systems. These devices help to ensure consumers stay on schedule with changing of replacement elements and alert them if a system failure is detected. These performance indicating, sensing and monitoring devices are especially beneficial in situations where the system is being relied on to reduce health effects contaminants that cannot be seen, smelled or tasted.

Performance requirements
The NSF Joint Committee on Drinking Water Treatment Units (DWTU) has recognized the proliferation and benefits of performance indicators, and has incorporated requirements for them into a number of the ANSI/NSF DWTU standards. These requirements are summarized in Table 1.

Because of the various scopes of standards in terms of technologies and contaminant reduction capabilities, the requirements for performance indicators vary significantly from standard to standard. Standard 42: Drinking Water Treatment Units—Aesthetic Effects and Standard 44: Residential Cation Exchange Water Softeners don’t address performance indicators. Because Standard 42 addresses only aesthetic contaminants, any failure of the system will be noticeable by the users through undesirable tastes, odors or other characteristics—it won’t lead to any adverse health consequences. Cation exchange water softeners regenerate regularly and don’t have replaceable treatment components as many of the other technologies do. As long as salt is available in the brine tank, the water softener can operate for years without any further maintenance. As such, performance indication requirements aren’t included in Standard 44.

Standard 53: Drinking Water Treatment Units—Health Effects, however, addresses health effects contaminants, and most Standard 53 devices require replacement of treatment elements regularly. For this reason, Standard 53 makes provisions for performance indicators, although it doesn’t require them. Systems that make chemical reduction claims are tested to 120 percent of capacity if they incorporate a performance indicator, and 200 percent of capacity if they don’t. This requirement benefits manufacturers who incorporate a performance indicator into their systems in two ways. First, a system must be tested less, which results in lower testing costs if it incorporates a performance indicator. Second, a device that’s tested to failure can be certified and marketed to a higher chemical reduction capacity if it includes a performance indicator. See Table 2 for an example of these benefits.

Many types of performance indicators are acceptable under Standard 53. They may flash a light, sound an alarm, stop the flow of water or all of the above. They must, however, be incorporated into the device itself. A sticker that a consumer puts on a calendar as a reminder to change the filter isn’t considered to be a performance indicator under Standard 53. It also requires a test of the performance indicator to verify that it works—and works accurately. The performance indicator must be tested to activate between 80 percent and 110 percent of its intended activation point.

Standard 55: Ultraviolet Microbiological Water Treatment Systems also addresses health effects through Class A systems, which can be used to inactivate and/or remove microorganisms from contaminated water. Therefore, Standard 55 Class A systems must include performance indicators. Class B systems, used for non-pathogenic nuisance organisms only, may include performance indicators, but aren’t required. Standard 55 requires any system that includes a performance indicator must have the performance indicator tested. This test requires that the indicator must successfully activate 100 consecutive times when the UV transmittance through the system is decreased below effective levels.

RO can do the job
Reverse osmosis (RO) systems are also capable of reducing health effects contaminants in drinking water. Consistent with the philosophy of performance indication in other standards, Standard 58 also has requirements for performance indication. Any system that conforms to ANSI/NSF 58 for the reduction of health effects contaminants must provide the user with an effective means of warning if the system isn’t functioning properly. This can include a performance indicator built into the system, or a sampling and analysis service or kit used to verify the quality of the treated water. Unlike Standards 53 and 55, there’s no requirement or protocol to test the effectiveness of a performance indication device for an RO system that conforms to Standard 58.

Standard 62: Drinking Water Distillation Systems also includes a requirement for performance monitors, as distillation systems have the capability to reduce health effects contaminants. Any distillation system that claims reduction of health effects contaminants must include a performance indicator to conform to ANSI/NSF 62. Further, conforming distillation systems making claims for microbiological reduction or nitrate reduction must be equipped with an automatic shutdown or diversion of distillate to waste if system failure occurs. Performance indication of distillation systems is usually based on monitoring of total dissolved solids (TDS). Standard 62 includes a protocol for verifying shutdown or distillate diversion for performance indication devices based on TDS levels. The standard also requires that any other technology for monitoring performance of systems making health effects claims must be verified, although protocols for validating the performance of these monitoring devices aren’t included.

Much like today’s cars, many modern residential drinking water treatment systems incorporate monitoring devices to help keep consumers safe. Most health effects contaminants that could be present in drinking water at unsafe levels aren’t detectable through appearance, taste or odor. The presence of these contaminants isn’t easily noticed by consumers, which underscores the importance and benefits of performance indicators. Recognizing the importance and benefits of these devices, the NSF Joint Committee on DWTUs has incorporated requirements and test protocols into the standards. As a result, just as I’m safer from mechanical breakdowns and running out of gas in my modern car with its monitoring capabilities, consumers of treated drinking water are safer from system failures or maintenance neglect through the incorporation of performance indicating monitoring devices.

About the author
Rick Andrew is the technical manager of the Drinking Water Treatment Units program at NSF International. He has been with NSF for four years. His previous experience was in the area of analytical and environmental chemistry consulting. Andrew has a bachelor’s degree in chemistry and a master’s degree in business administration from the University of Michigan. He can be reached at email:


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