CONCERNS ABOUT drinking water quality have led consumers to purchase a variety of products to treat their water, from hand-held pitchers or faucet-mounted filters to in-line water softeners and reverse osmosis systems.

"Certified to ANSI/NSF Standard" assures state regulators, retailers, food service professionals, and consumers of the integrity and functionality of drinking water treatment products.

However, most consumers make such purchases without knowing exactly what products are available and which best fit their needs and budget. This article reviews the six ANSI/NSF standards for drinking water treatment units, summarizing the systems they cover, the sections common to all standards, and the kinds of performance claims that NSF-Certified products can make.

Standards 42 and 53
Drinking Water Treatment Units – Aesthetic and Health Effects
Standard 42 and 53 certify mechanical and carbon filtration systems. Standard 42 deals with aesthetic claims such as chlorine, taste and odor, and bacteriostatic claims. Standard 53 covers health claims such as lead, volatile organic compounds, cyst, and the gasoline additive MTBE.

Standard 44
Residential Cation Exchange Water Softeners
Standard 44 covers water softeners, testing for items such as hardness reduction, radium and barium reduction, and efficiency ratings.

Standard 55
Ultraviolet Microbiological Water Treatment Systems
Standard 55 covers two classes of ultraviolet treatment systems:

Class A systems meet the requirements to disinfect and/or remove microorganisms from contaminated water, including bacteria and viruses, to a safe level.

Class B systems are designed for supplemental bactericidal treatment of treated and disinfected public drinking water or other drinking water deemed acceptable by a local health agency.

Standard 58
Reverse Osmosis Drinking Water Treatment Systems
Standard 58 certifies reverse osmosis (RO) units. RO systems have the added benefit of combining carbon filtration with RO technologies. The standard covers reduction claims such as fluoride, hexavalent and trivalent chromium, TDS, and nitrate/nitrite reduction.

Standard 62
Drinking Water Distillation Systems
Standard 62 covers the claims distillation systems can make related to reduction of mercury, nitrates and nitrites, arsenic, and microbiological performance.

Testing and Evaluation
All standards are divided into seven sections, with the essential testing and evaluation in Sections 4 through 7.

Section 4: Materials in Contact with Drinking Water
Each material exposed to drinking water must be reviewed to ensure that nothing with detrimental health effects is leaching out into the drinking water. For each wetted part, formulation information must reference the Code of Federal Regulations Title 21 (CFR 21).

Once NSF receives all formulation information, a toxicologist reviews the ingredients in each component to determine what analytes need to be examined during extraction testing. The extraction water is then collected and analyzed for the specified contaminants. Final extraction results are forwarded to the toxicologist to compare them against current allowable levels.

In addition to current allowable levels, ANSI/NSF standards set "Advisory Concentrations" for some contaminants that are lower than the nationally regulated levels.

Section 5: Design and Construction
Section 5 establishes pass/ fail requirements for testing to ensure that a correctly installed unit will operate properly under the pressure rating claimed by the manufacturer. Standards 42 and 53 set requirements for hydrostatic pressure, burst pressure , and cyclic pressure testing. Depending on the system and the rated pressure of the unit, each system may need some, if not all, of these tests.

For reverse osmosis products, Standard 58 is more detailed, including items such as flow control, reject water air gap connections, performance ratings, and storage tank capacity. The standard also sets requirements for nitrate/nitrite and arsenic reduction claims.

Arsenic claims must indicate that these systems be used on water supplies maintaining detectable residual free chlorine. Nitrate/nitrite systems must have either a monitor on the product water stream or include an analysis kit with the system.

Section 6: Chemical and Mechanical Performance
All systems certified to the DWTU Standards must meet material extraction and structural integrity requirements. However, Certified systems are not required to meet all reduction claims covered in Section 6.

For example, simple systems designed to remove chlorine, taste and odor can be manufactured at a low cost and certified in a short period of time. Conversely, systems designed for extended claims such as MTBE, TTHM, and cyst reduction for Cryptosporidium and Giardia involve more engineering and typically incur more costs to manufacture and certify.

Section 7: Product Literature
Section 7 sets specific requirements for product literature, including installation, operation, and maintenance instructions; specifications on the data plate; and literature on replacement components.

Section 7 also requires a performance data sheet, which gives a quick summary of that system's requirements and reduction testing information. The performance data sheet was developed by the DWTU Joint Committee to give consumers information so they can make more informed buying decisions.

DWTU v. Standard 61: Material Extraction
DWTU extraction protocol requires conditioning according to the manufacturer's use instructions, followed by three 24-hour extraction periods. The testing protocol in DWTU standards differs from that of ANSI/NSF Standard 61, where many of the sections have an extended conditioning period.

Section 8 of Standard 61, which covers mechanical plumbing devices such as pumps, valves and tanks, requires a 14-day conditioning period with 10 water changes. After the initial conditioning period, there is another two-day conditioning before samples are collected.

This extended conditioning is mandated in Standard 61 because many products installed in a potable water system have an extended life of 10 years or more. Drinking water treatment units, however, are usually designed to last a specific period of time, typically not to exceed one year, before the user is directed to replace the filter cartridge.

DWTU standards also require extraction testing under line pressure, while the Standard 61 exposure protocol is not under line pressure. DWTU materials are also required to be CFR 21 compliant (or equivalent).

Under DWTU standards, components can be certified for material extraction; pressure-bearing components can also be certified for structural integrity. A significant number of component manufacturers already have products certified, easing the certification process for system manufacturers.