By Rick Andrew
NSF/ANSI 44 Residential Cation Exchange Water Softeners has long been the American national standard for evaluation of water softeners. This standard has created a level playing field for testing and establishing capabilities, such as softening capacity and salt and water efficiency. It has also helped manufacturers, dealers and retailers assure that their products are safe for contact with drinking water, structurally sound and helped consumers buy products with confidence.
Over the last 20 years or so, we have seen the emergence of other technologies designed to perform a function of scale control in residential settings. These technologies include magnetic, electromagnetic, various types of media, physical devices, chemical addition and more, but they all have one thing in common: they are not cation exchange. And as such, there has not been any American national standard for evaluating them.
German Standard DVGW W512
The Deutscher Verein des Gas und Wasserfaches (DVGW) (German Association for Gas and Water) published their technical rules W512 in 1996 to evaluate non-cation exchange scale control technologies. The test protocol in these technical rules includes introducing hard water to the scale control device and then into a small electric hot-water heater. The protocol requires testing in duplicate and also includes duplicate controls consisting of parallel paths of untreated, hard water into identical heaters. After the operational period, the amount of scale formed in the control hot-water heaters is compared to the amount of scale formed in the hot-water heaters downstream of the two test units. An 80-percent reduction of scale formation is required.
There have been some criticisms of the test protocol within DVGW W512. These criticisms have typically centered around the operational protocol itself and the amount of water drawn and timing of the drawing of water, as well as the power output of the heating elements within the water heaters. Additionally, the protocol does not include any plumbing downstream of the water heaters where additional scale formation could occur.
In 2007, the International Association of Plumbing and Mechanical Officials (IAPMO) filed a Project Initiation Notification System (PINS) notification with ANSI to significantly revise IAPMO Z601. Prior to this time, IAPMO Z601 Scale-Reduction Devices featured a limited scope and did not address the actual scale reduction performance of the devices. The filing of the PINS in 2007 served notice that the standard would be modified to add those requirements. The effort to do this was headed up by the IAPMO Z601 Technical Subcommittee, working under the IAPMO Plumbing Standards Committee. Participation on the subcommittee included a crosssection of manufacturers, regulators, consultants and certifiers, including IAPMO, NSF and WQA. The group basically started with the concept pioneered by DVGW W 512 and worked to update and enhance it through a consensus process. This work took several years and ultimately resulted in a draft that was ready for validation testing in 2014. NSF undertook validation testing earlier in 2014 and shared results with the technical subcommittee. Based on the validation testing and approval by the technical subcommittee and the IAPMO Plumbing Standards Committee, IAPMO put the standard out for public comment. The public comment period ended August 25. Two people submitted comments during this period. (As of the writing of this article, the comments are being responded to, and it is expected that IAMPO Z601 will officially be published as soon as the end of October.) Scope and end uses IAPMO Z601 covers basically any technology capable of reducing scale in plumbing in residential and similar applications utilizing traditional gas and electric hot-water heaters. Commercial recirculating boiler-type applications and any application involving multiple passes through the device are not within the scope of the standard. Use in a plumbing system upstream of tankless water heaters is also not currently covered by IAPMO Z601.
For those devices that include parts in contact with potable water, material safety through material formulation review and extraction testing to NSF/ANSI 42 or NSF/ANSI 61 is required. Some products, such as RF induction coils, do not contact potable water, so there is no material safety requirement for these technologies. For those devices requiring electricity to operate, evidence of conformance to the appropriate electrical safety standards is required. Devices that release chemicals into the water must conform to the appropriate requirements in NSF/ANSI 42 or NSF/ANSI 60, as appropriate, to assure the chemicals
are safe for use in potable water at the concentrations used.
Devices that are pressurized with potable water must meet the
structural integrity requirements of NSF/ANSI 42.
The scale-reduction testing approach under IAPMO Z601 uses four parallel paths for flow of hard water, two of which have the scale-reduction device inline and two of which are controls. The water has hardness of 26 ± 3 grains per gallon, with calcium making up 75 to 85 percent of the hardness and magnesium making up the rest. The exact test operation depends on the technology being evaluated. The first consideration is whether the device significantly changes the chemical characteristics of the water. These changes could be changes to the pH, the hardness, the concentration of phosphates or silicates, or other changes to the water. Technologies that change the characteristics of the water include water softeners and other devices that regenerate, devices that release chemicals from sacrificial media or media with a limited treatment capacity, or devices that perform direct injection of treatment chemicals. The standard includes requirements for the evaluation of the treatment capacity associated with devices of these types. Additionally, the standard includes requirements to evaluate the safety of the chemicals at the concentrations released in potable water for devices incorporating sacrificial media or direct injection of treatment chemicals.
Evaluation of treatment capacity aside, the basic testing protocol for devices that do not significantly change the chemical characteristics of the water involves first conditioning the two test-unit devices with recirculated test water for two hours. This water is analyzed to confirm that the devices are not significantly changing the characteristics of the water. Then the test stand is thoroughly cleaned to assure that there are no films or deposits present. The test rig incorporates four parallel water pathways, each with a small (10-liter) electric water heater with electric heating elements (two pathways will have test units installed upstream of the heaters and two are controls with no device upstream). The standard specifies testing at various power densities in these heating elements depending on the intended end use (see Figure 1). The power density for testing is selected by the manufacturer. The two conditioned test-unit devices are then installed on the test stand. The standard additionally requires that each of the pathways on the test stand include a 15-meter coil of austenitic stainless steel tubing (austenitic stainless steel has an austenite form, meaning it has chromium and nickel as part of the composition) downstream of the heaters. See Figure 2 for a photo of a test stand.
A daily operational schedule of flow was designed based on typical water usage patterns for a family of four. This schedule includes flowing water through the test unit devices 36 times each day, with varying flowrates and duration of flows, to simulate various usage events: showers, baths, toilet flushing, faucet operation, etc. A total of 916 liters of water per day is flowed. For each event, 3.8 liters of the water is passed into each water heater, with the rest diverted to drain. The daily operational scheduled is continued for at least 20 days.
At the end of the test period, the test stands are drained and any loose scale is collected. Then, the test stands (including the 15-meter coil of tubing downstream of the heater) are acid washed. The total loose scale and scale removed through the acid washing protocol is established for each of the four pathways in the test stand. The average mass of scale from the two treated pathways is compared to the average mass of scale in the two untreated pathways. An 80-percent reduction of scale is required. It is possible that the test devices may also affect the controls, such that they limit scale formation in the control even though they are not directly installed in the control pathways. If the scale formed in the controls is low compared to a previously conducted calibration run, then a separate run without the test unit devices is conducted to establish the control for testing purposes.
A new tool for evaluation
With the completion of IAPMO Z601, there is now a new tool for evaluation of a variety of technologies that previously did not have a consensus standard method for evaluating them. Given the emergence of many of these technologies in the marketplace, it is hoped that this new tool will be a powerful one for manufacturers, dealers, retailers and consumers alike, in assessing the value and effectiveness of these technologies and products.
About the author
Rick Andrew is NSF’s Director of Global Business Development–Water Systems. Previously, he served as General Manager of NSF’s Drinking Water Treatment Units (POU/POE), ERS (Protocols) and Biosafety Cabinetry Programs. Andrew has a Bachelor’s Degree in chemistry and an MBA from the University of Michigan. He can be reached at (800) NSF-MARK or email: Andrew@nsf.org