By Rick Andrew

Most US states have regulations in place that require materials in contact with drinking water in the distribution system to conform to NSF/ANSI/CAN 61. These regulations typically have a broad scope, including essentially all materials from source to tap. POU and POE treatment systems are among very few exceptions because they are covered by the NSF/ANSI Drinking Water Treatment Unit standards. By requiring this conformance, the states are well positioned to ensure that these materials will not contribute harmful levels of contaminants to drinking water. Products (including well casings, water intakes, pumps, valves, coatings, pipes, fittings, gaskets and more), when used in a water distribution system, are covered by these regulations. Each of these products likewise has evaluation methods included in NSF/ANSI/CAN 61.

One material among this category of product is somewhat a special case. Concrete is frequently used to construct large water holding elements of water distribution systems. These mixtures include natural materials sourced from sites that are typically near the area where the concrete structure is being built. Due to differences in the structures themselves, as well as the local geography, there is variability in these natural materials, as well as in the product composition and also the method of preparation of the concrete.

Despite these variations, most states state and many local authorities have these regulations in place that require that concretes used in large water storage tanks, reservoirs and pipelines conform to NSF/ANSI/CAN 61. Fortunately, there are procedures included in the standard to test and evaluate concrete site mixtures to establish this conformance.

Testing and evaluation process
The standard requires that the concrete supplier must provide the formula for the specific concrete mixture, including all cements, aggregates and admixtures. Based on this formula, an appropriate analytical test battery is developed for the concrete, according to the procedures spelled out in NSF/ANSI/CAN 61.

Once the test battery is established, the concrete supplier submits cylinder samples of the concrete to the laboratory. These cylinder samples are cured for at least 28 days, unless otherwise directed by the concrete supplier. After curing, the cylinders are put on test and exposed to the specific test water as specified in the standard. At the end of the exposure, the final test water is then analyzed according to the analytical battery that was developed based on the characteristics of the formula for the mixture. Any potential contaminants that leach from the cylinders are analyzed, quantified and evaluated for toxicological significance according to the requirements of NSF/ANSI/CAN 61.

All of the test results, data and assessment of conformance to the requirements of the standard are included in a test report. Additionally, the assumptions for the end use of the material are considered, such as the volume of water per surface area of the concrete that will be applicable based on the concrete structure that is being built. The test report includes a statement indicating whether the concrete site mix conformed to the requirements of NSF/ANSI/CAN 61. The concrete supplier then uses the letter to demonstrate conformance to the relevant state or local authorities.

Meeting the needs of end users
This approach to evaluating concrete site mixtures provides a quick, reasonably priced solution for concrete suppliers to demonstrate conformance of their concrete mixtures to NSF/ANSI/CAN 61. In turn, state and local authorities have a straightforward way to assure that concrete projects are meeting the requirements of regulations and also can have confidence that the drinking water stored in these concrete structures will be safe.

It is important to note that this approach to evaluation of concrete site mixtures is a ‘test only’ approach. Test only, as opposed to certification, makes sense for concrete site mixtures because the evaluation is in support of construction of a specific concrete structure that will be built one time. The ongoing surveillance and assurance of continuous manufacturing quality that certification provides for manufactured products does not really apply in this unique case of concrete site mixes.

So, this test’s only approach of establishing conformance does not constitute certification to NSF/ANSI/CAN 61. Because of the variability in natural materials and concrete mixtures, the resulting test report is only valid for the particular project for which the specific concrete cylinder was tested. This test report does not give the concrete supplier the ability to claim conformance to NSF/ANSI/CAN 61 for any other concrete site mixtures.

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

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