Water is important. It makes up 60% of your body and 71% of your planet’s surface. In fact, in the over-dozen times we’ve focused on drinking water standards in this blog, their purpose has been clear: drinking water needs to be safe for consumption to support public health. Aiding the performance of treatment units that minimize the health effects of drinking water, NSF/ANSI 53-2021: Drinking Water Treatment Units – Health Effects outlines various requirements.
American National Standard for Drinking Water Treatment Units
Units that reduce health-related contaminants in drinking water are one of the final bulwarks that protect the public from harm.
Specifically, NSF/ANSI 53-2021 establishes minimum requirements for materials, design and construction, and performance of drinking water treatment systems designed to reduce specific health-related contaminants in public or private water supplies. These systems, point-of-use (POU) and point-of-entry (POE), reduce substances considered established or potential health hazards, whether chemical or particulate in nature. This includes radon, asbestos, Cryptosporidium oocysts, and inorganic volatile chemicals, among numerous other contaminants listed in tables in the standard.
NSF/ANSI 53-2021 applies to systems can be used to treat all or part of the portable water at the inlet to a residential facility or a bottled water production facility, and the standard includes the materials and components of these systems.
The standard also includes product literature and labeling information.
Changes to NSF/ANSI 53-2021
Compared to the previous edition from 2020, NSF/ANSI 53-2021 has undergone the following changes of note:
- The minimum air gap requirement for drinking fountain outlets was revised from 2 inches to 1 inch.
- Specification was added noting that tannic acid can be used per Annex N-7, “Preparation of TOC solution using tannic acid,” to achieve a consistent level of total organic carbon (TOC) in the starting test water when it can not be achieved from the natural water.
- 1,2,3-trichloropropane was added to the chemical reduction claims.
- Language was corrected to indicate that batch systems sampling is to be taken when the filling time is increased by 33%, 100%, and 300%.
- The acceptance criteria for the microsphere test was clarified to pertain to every effluent sample point in Sections 22.214.171.124.1, “Polystyrene microsphere reduction claim for systems other than those used in bottled water plants,” and 126.96.36.199.1, “Polystyrene microsphere reduction claim.”
- Section N-1.6.1, which covers sample collection for Cryptosporidium parvum oocysts, was corrected with regard to the polyoxyethelene sorbitan mono-oleate concentration and removed the requirement to collect influent samples in triplicate.
- The minimum 2-L sample requirement was updated to a requirement.
- Corrections were made to terminology.
- References were updated.
- An analyte was added to Table 4.2, “Extraction testing parameters (semivolatiles),” and Table 8.1, “Performance data sheet reduction claims.”
- Evaluation criteria for n-nitrosamine removal were added as new Section 7.2.7, “N‐nitrosodimethylamine (NDMA) reduction testing,” and new Informative Annex 7, “Explanation of scope and purpose of N-nitrosodimethylamine (NDMA) reduction claim.”
- Two instances of Pb(NO3) were corrected to Pb(NO3)2 in Section 188.8.131.52.2.3.1, which covers the preparation of the solutions for generating the lead pH 8.5 test water.
- A column was added for the individual influent sample point limit to Table 7.13, “Mercury reduction requirements.”
NSF/ANSI 53-2021: Drinking Water Treatment Units – Health Effects is available on the ANSI Webstore.
Drinking Water Treatment Units Aesthetic Effects
For guidance on drinking water treatment units the reduce the presence of aesthetic contaminants, please refer to our post NSF/ANSI 42-2021: Drinking Water Treatment Units, Aesthetic Effects.
Past Revisions of NSF/ANSI 53
Due to the sheer importance of drinking water, this American National Standard developed by NSF International is published annually. If you need any past editions of ANSI 53, you can find them as historical standards on the ANSI Webstore. You can also read about the many changes made to past revisions below:
Changes to NSF/ANSI 53-2020:
- A new statement was added for conditioning and conditioning volumes for microcystin reduction claims.
- The test pressure for nonpressurized water treatment devices was clarified.
- Guidance on extraction testing for hot and cold water dispensers was added.
- An exemption was added for cyclic pressure testing for components downstream of the system on/off valve that are not subject to pressure under the off mode and either contain no media subject to pugging or are not designed to contain media.
- Clarification was provided on how systems shall be tested with and without adsorptive or absorptive for replacement elements.
Changes to NSF/ANSI 53-2019:
- A performance reduction claim was added for perfluorocctanoic acid (PFOA) and perfluoroctane sulfonate (PFOS) for nonregenerable drinking water treatment devices that use anion exchange media. This is found in new section 7.2.6, “Nonregenerating PFOA/PFOS reduction testing.”
- The pass/fail criteria for lead reduction (Tables 7.10 and 8.1) was changed from 10 μg/L to 5 μg/L. This alteration reflects proposals at the state, federal, and international levels.
- A previous error in Table 5.1, “Structural integrity testing requirements,” was corrected, adding a heading for “Complete systems” and “Components.”
- Keeping in line with editorial changes to made to many NSF standards published in 2019, the annexes were changed from alpha characters to numeric and are now preceded by “Normative” or “Informative.” For example, “Annex A” from NSF/ANSI 53-2018 is called “Normative Annex 1 (N-1)” in NSF/ANSI 53-2019.
Changes to NSF/ANSI 53-2018:
- An asbestos reduction protocol was added for batch treatment systems in Section 7.3.1, “Asbestos reduction claims.”
- The standard clarified language on systems that include components or functions covered under other NSF standards.
- This revision clarified “product literature requirements” under Section 8.3, “Replacement components.”
- For drinking water treatment devices that use activated carbon absorption, this edition of the standard added a performance reduction claim for perfluorocctanoic acid (PFOA) and perfluoroctane sulfonate (PFOS).
Changes to NSF/ANSI 53-2017:
- Sample collection for systems containing multiple potable water outlets under 4.2.3, “Exposure” were addressed.
- Evaluation criteria columns from Tables 4.1 – “Extraction testing parameters (metals),” 4.2 – “Extraction testing parameters (semi-volatiles),” and 4.3 – “Extraction testing parameters (volatiles)” were removed and instead referenced the evaluation criteria in Annex D Table D.1 in NSF/ANSI 61.
- Performance guidelines for drinking water treatment systems designed to reduce microcystins in public water supplies were added.
- New normative Annex J, “Preparation of TOC solution using tannic acid.”
- New informative Annex K, “Explanation of scope and purpose of microcystins reduction claim.”
Changes to NSF/ANSI 53-2016:
- Language was added to state that systems be conditioned using the test water with the specified contaminant for chemical reduction claims.
- CAS numbers were added to Table 4.1 (previously Table 1) of the materials evaluation criteria.
- Sampling point instructions for squeeze bottles in Annex E were clarified.
- Tables were changed to reflect the appropriate section in which each is located.