Guidance for Compliance with NSF/ANSI Std 61 In Drinking Water Systems


Revision 2   -  NSF/ANSI Std 61 was adopted January 2017

After analysis of results provided over a five-year period on cement and concrete testing, the following criteria were added to NSF/ANSI 61: 

  • Clarification that concrete aggregate testing is optional;
  • Establishment of surface area to volume ratio for concrete; and
  • Addition of criteria identifying when the testing of concrete isn’t required under NSF/ANSI 61.

The revised standard includes Table 5.6 that summarizes the surface area-to-volume ratios for tanks or storage vessels.  The testing of concrete, aggregate, or cement is not required under NSF/ANSI 61 when the surface area-to-volume ratio is less than or equal to 0.8 in2/L or 0.08 in2/L for static or flowing conditions respectively.

In summary, concrete tanks that are 350,000 gallons or greater in volume have a surface area-to-volume ratio is less than or equal to 0.8 in2/L therefore do not require testing for concrete, concrete aggregate, or Portland and hydraulic cements.  Admixtures used in the design need to be compliant with STD 61.  STD 61 admixes have been readily available in the industry.

As noted: The addition of the criteria for concrete water storage structures is in recognition of the diminishing value of investigations on those with high volumes (low surface area-to-volume ratios) where admixtures have separately been verified as compliant with this standard and the water storage structure is separately monitored for regulated contaminants including radionuclides.

The standard was revised as proposed in January 2017. The ballot summary  shows the vote tally approving the language as proposed in gray on the ballot (pdf.) The revised standard was published 03/13/2017 and can be purchased through NSF at https://www.techstreet.com/nsf/standards/nsf-61-2017?gateway_code=nsf&product_id=2002820#jumps.


Background

The State of California’s Title 22 Drinking Water Standard Section 64591 states: “after March 9, 2008 a water system shall not use any chemical, material, lubricant, or product in the production, treatment or distribution of drinking water that will result in its contact with drinking water... that has not been tested and certified as meeting the specifications of NSF International/American National Standard Institute (NSF/ANSI) 61-2005/ Addendum 1.0 - 2005 (Drinking Water System Components - Health Effects.)”  

An ad hoc subcommittee was formed in late 2012 to address a recurring subject at CANV AWWA conferences brought forth by utility owners, consultants and manufacturers alike that is challenges complying with NSF/ANSI Standard 61 concrete and other materials used in drinking water systems.

The subcommittee formed a working group and worked with the California Division of Drinking Water (known as CA Department of Public Health when the efforts began) to insure there is clarity in the process for insuring compliance with Standard 61 and that the materials used are equally as protective of public health.   In addition, the group engaged with California Construction and Industrial Materials Association (CALCIMA) for their input and expertise on product availability and testing for concrete and individual components from suppliers.

The group has finalized guidance and developed sample specifications for concrete in direct contact with potable water NSF-ANSI Std 61 Guidance.  In addition, the group has confirmed when performing soak tests on aggregate materials it is acceptable to NSF to perform tests on the smallest aggregate since it has the highest surface area to volume ratio. Letter from NSF.