By Monica Leslie, MPH
In May 2001, the NSF Joint Committee on Drinking Water Treatment Units (DWTUs) supported the development of a new standard to address shower filter systems.
A uniform approach
Inquiries made to NSF by the industry, consumers and regulatory agencies indicated the need for establishment of uniform testing methods to evaluate the effectiveness of such systems. The new standard, ANSI/NSF 177-Shower Filtration Systems, will meet this goal by establishing minimum performance requirements for such units, including contaminant reduction performance, materials safety, design and construction, and structural performance. Similar to all other DWTU standards, this standard will also specify the minimum product literature and labeling information that a manufacturer shall supply to authorized representatives and system owners.
Under the direction of the DWTU Joint Committee, a task group was formed in July 2001 with volunteers from the joint committee, manufacturers from the shower filter industry and other interested parties, such as Water Quality Association and Health Canada. The goal of the task group is to address the issues that may be unique to a shower filtration system, and make recommendations to the DWTU Joint Committee regarding the criteria and testing methods used for evaluating a system’s performance.
Setting the criteria
At its first two meetings, which took place in October and December 2001, the task group identified several key issues that need to be addressed within the standard. First, the task group determined that initially the scope will apply to shower filtration systems designed to reduce specific chemicals affecting the aesthetic quality of water used for bathing. Claims for the reduction of health effects contaminants, including biological, chemical, physical or radiological, wouldn’t be included under the initial scope of the standard. After further consideration, the group reached consensus that the standard initially would only address systems intended to reduce free available chlorine (FAC). The task group agreed, however, that as new technology warrants — and further test methods and criteria are developed — other substances that are also at concentrations influencing public acceptance of water for bathing could be included as well.
Second, the task group agreed that, although shower filtration systems aren’t intended to serve as drinking water treatment units, these systems are in contact with potable water and therefore shouldn’t impart extractable contaminants such as heavy metals and volatile organic compounds (VOCs) into the water. The task group decided to consider an abbreviated materials evaluation method that would include substances that have maximum contaminant concentrations (MCCs) and maximum drinking water levels (MDWLs) only. The proposed test, which would be performed on two systems, would include flushing each system for a minimum of 10 minutes (or per the manufacturer’s recommended time, if longer) using a public water supply with the following characteristics:
- pH of 6.75 ± 0.25;
- Temperature of 40°C ± 2°C (104°F ± 4°F);
- Total dissolved solids (TDS) of 50 mg/L ± 5 mg/L, and
- Free available chlorine (FAC) concentration of 0.5 mg/L ± 0.05 mg/L.
After flushing, each system would be refilled with exposure water and maintained for 10 minutes at a temperature of 40°C ± 2°C (104°F ± 4°F). A 1-liter sample would then be drawn from each system, composited and analyzed. For those systems containing metallic-based media, an additional 1-liter sample will be collected from each system at the completion of the performance test, composited and analyzed for those metals. Evaluation of materials would apply to systems that include one or more showerheads, as well as those that supply the filter unit alone. For systems that include more than one type of shower-head, all showerheads would require extraction testing, depending upon the type of materials from which they’re made. As an alternative to testing, the task group agreed that a manufacturer could also choose to use materials certified to ANSI/NSF Standard 61: Drinking Water System Components-Health Effects.
Task group participants also agreed that a shower filtration system would be verified for design, construction and structural performance. One possible requirement would be that a system be designed and constructed to maintain structural integrity at a minimum working pressure of 690 kilopascals (kPa), or 100 pounds per square inch gauge (psig). A hydrostatic pressure test would be conducted by testing the system under 1.5 times the maximum working pressure for a system designed for open discharge, and three times the maximum working pressure for a system with a pressure vessel upstream of a filter. A cyclical pressure test would also be performed at 10,000 cycles at 0-345 kPa (0-50 psig) or 100,000 cycles at 0-1,040 kPa (0-150 psig), depending upon whether the system is designed for open discharge or with a pressure vessel upstream of a filter, respectively. It was proposed that both tests be performed at a temperature of 49°C (120°F).
Finally, the initial test method and acceptance criteria for FAC reduction were discussed by the task group. After much consideration, the majority of members proposed that a shower filtration system be required to reduce an influent challenge concentration of 2.0 milligrams per liter (mg/L) by a minimum of 50 percent. If a manufacturer’s system exceeded the 50 percent minimum reduction of FAC during testing, the manufacturer could also state the actual performance results on its packaging and product literature. A system would be tested using the test water specified above at an initial dynamic pressure of 552 kPa (80 psig), and would be operated on a 15-minute on, 15-minute off cycle, 16 hours per day, with an 8-hour rest period. Collection of the effluent water samples would occur in a closed system. Discharge would be sent through a collection tube, reducing the volatilization of any potential FAC into the atmosphere. Samples would be collected at the end of each 15-minute “on” portion of the cycle at various points of the estimated system capacity. The proposed test, which would be performed on duplicate systems, would be similar in many ways to the chlorine reduction test method currently in ANSI/NSF Standard 42: Drinking Water Treatment Units-Aesthetic Effects (see Table 1).
Another meeting of the task group was scheduled for March 2002. The group is expected to finalize the specific test protocol for FAC reduction and continue to discuss materials safety, structural performance and labeling requirements. Once the task group participants have reached consensus on these issues, it’s anticipated that a draft standard will be ready for the DWTU Joint Committee to review later this year.
About the author
Monica Leslie is a project manager for drinking water standards in the Standards Department at NSF International. She earned her master’s degree in public health from the Northwest Ohio Consortium for Public Health, offered jointly by the Medical College of Ohio, University of Toledo and Bowling Green State University. She can be reached at (800) 673-6275 or email: [email protected].