By Rick Andrew
NSF/ANSI 44: Residential cation exchange water softeners describes requirements for material safety, structural integrity, pressure drop, capacity, efficiency, brine accuracy and product literature for POE cation exchange water softeners. As such, it is a comprehensive document addressing many relevant aspects of these systems. NSF/ANSI 44 was, however, developed some years ago and there are certain trends in the technology that could probably be better addressed by the standard. This column will examine the current requirements, and also look at some of the areas for future development to address newer softeners.
Current requirements
Material safety
NSF/ANSI 44 requires that safety for drinking water contact for materials is established through extraction testing. The softener is first flushed and conditioned, then exposed to water with specific characteristics under specific conditions. The water is collected and chemically analyzed. Different types of water are used to evaluate potential leaching of various contaminants. Softeners that include activated carbon are evaluated without the activated carbon, and the activated carbon itself is also evaluated. Any contaminants detected are evaluated for toxicological significance.
Structural integrity
The standard requires that softeners must be able to maintain watertightness when hydrostatically tested for 15 minutes at 300 psi, or 2.4 times the manufacturer’s pressure rating, whichever is higher. A cyclic test is also required, specifying 100,000 cycles of zero to 150 psi.
Pressure drop
A softener may have no more that 15 psi pressure drop at the manufacturer’s rated service flow. A test is required to confirm this.
Capacity
The softener is regenerated with the specific amount of salt specified by the manufacturer, and then hard water at 20 grains per gallon is softened at 50 percent of the manufacturer’s rated service flow. Once the softened water reaches one-grain-per gallon hardness, the capacity of the softener at the specified salt setting has been reached.
Efficiency
The NSF/ANSI 44 efficiency rating includes efficiency in both salt usage and water usage for regeneration. In order to qualify as an efficiency rated softener, the softener must be able to remove 3,350 grains of hardness per pound of regenerant salt and must use no more than five gallons of water per 1,000 grains of hardness removed for regeneration. Note that efficiency ratings apply only to operation with specific amounts of regenerant salt. That is, a softener that is efficient at some salt settings likely will be less efficient at other (higher) salt settings.
Brine accuracy
The brine system must deliver salt at each manufacturer’s specified salt setting accurately—within 15 percent of the nominal value.
Product literature
Softener systems must include a data plate permanently affixed to the softener that includes basic information, such as the manufacturer’s name; a performance data sheet detailing specifications of the softener (such as rated service flow and information related to efficiency for efficiency-rated systems) and a manual that includes information, such as ongoing maintenance requirements.
A comprehensive standard, but…
Clearly, NSF/ANSI 44 addresses important issues associated with water softeners. As mentioned earlier, however, there are opportunities to advance the standard. Some of you may have already started thinking about them as you read through the current requirements. Some of these opportunities include:
- Requirements for replacement-cartridge softener systems. Right now, replacement-cartridge softener systems are not addressed by NSF/ANSI 44. In the last few years, there have been more and more of these products introduced to the market, primarily for use in commercial coffee brewing. NSF/ANSI 44 could be expanded to include requirements for these products.
- Addressing softeners with smart controls. Reading between the lines for the current requirements of NSF/ ANSI 44, it becomes clear that the standard was written with the idea that softeners include control valves with specific salt settings that are adjusted by the dealer or consumer. This concept is embedded in the way efficiency ratings are evaluated. In fact, the efficiency ratings are tied directly to specific salt settings.
But many newer softener control valves use electronic controls combined with flowmeters to gather and analyze data on water usage over time. These sophisticated control systems then analyze the data and adjust the regeneration of the softener according to an algorithm developed by the manufacturer. The Hard Facts about NSF/ANSI 44: Residential Cation Exchange Water Softeners Water Conditioning & Purification February 2013
In general, this type of technology is very good for the consumer. These types of controls mean that consumers are less likely to run out of soft water and that the softener will be regenerated efficiently in terms of salt and water usage, probably significantly more efficiently than with a control valve that always regenerates the softener with the same amount of salt.
There are some real challenges in expanding the standard to better address these systems. These challenges include:
- Manufacturers consider their operating algorithms to be proprietary and to be intellectual property. These algorithms may be providing them with a competitive advantage. So, discussing these operating algorithms in a standards-development environment becomes challenging.
- The softener will operate differently with different salt and water efficiency, depending on the pattern of water usage over time. The way these differences manifest for a given softener depends on the specific operating algorithm.
Dual-tank systems
Currently, dual cation ion exchange resin tank softeners are not specifically addressed by NSF/ANSI 44. This type of system can be used effectively to help assure that consumers do not run short of soft water at any time, and can enhance salt and water efficiencies over a system with one tank in other ways, too.
Proportional brining
NSF/ANSI 44 is written with the assumption that softeners will be operated until hardness breakthrough and exhaustion of the ion exchange resin’s capacity, and then fully regenerated. This is the way efficiency ratings are measured and calculated.Proportional brining systems, which regenerate prior to complete exhaustion of the ion exchange resin (i.e., prior to breakthrough of one grain per gallon hardness), are not specifically addressed under NSF/ANSI 44.
The challenges of keeping current
It is no small task to keep current with modern technology. We all see this in so many of our daily activities. Hopefully, we can all download some apps to our smart phones or tablets to help us as technology developments race forward at an ever faster pace!
The same is true of product standards. As products advance, so must the standards. Because standards are developed and advanced through a consensus process, with input from various affected stakeholder groups, it can be challenging to move fast enough to keep up with technology.
Fortunately, the NSF Joint Committee on Drinking Water Treatment Units is committed to keeping the NSF/ANSI DWTU Standards, including NSF/ANSI 44, up to date and relevant. They meet in person each year, and meet online and through conference calls in various working groups much more frequently. Their dedication and focus will benefit the entire industry as they work to assure these standards keep pace and remain relevant.
About the author
Rick Andrew is the General Manager of NSF’s Drinking Water Treatment Units (POU/POE), ERS (Protocols) and Biosafety Cabinetry programs. He previously served as the Operations Manager and, prior to that, Technical Manager for the program. 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: [email protected]