NSF/ANSI 50-2021: Equipment and Chemicals for Swimming Pools

Pools are as synonymous with summer as the beach, barbecues, vacation, and the hot sun. NSF/ANSI/CAN 50-2021, both an American National Standard and a National Standard of Canada, specifies information for not only swimming pools but also spas, hot tubs, and other recreational water facilities.

A Recent History on Swimming Pool Installations

In the United States, approximately 16 percent of all homes have a pool, a distribution that results from the pool market varying in accordance with certain influences over time.

2.1 million residential inground swimming pools were built between 1991 and 2006. This achievement is monumental when contrasted with preceding years. During this time, annual new pool installations shot up from 97,000 to 176,000. In fact, the 2.1 million inground pools built during this period equaled the entire number of pools installed since the emergence of the U.S. market in the 50s.

Reflecting on the latter half of the 20th Century, this information indicates substantial growth, but, when looking at the time since this inground installation boom, you can see a clear decline. In 2009, there were only 54,000 inground pools installed in the United States. The recession is largely to blame for this hit to the industry, but pool installations still have yet to return to their glory days.

Regardless, nearly 40 percent of all inground pools today were built between 1991 and 2006, placing a significance on the operation of existing pools.

Standard for Swimming Pool Equipment and Chemicals

Swimming pools are venues for recreation, but their installation and maintenance is subject to an assortment of codes, regulations, and standards that strive to assure reliability and limit hazards with their components and systems.

NSF/ANSI 50-2021: Equipment and Chemicals for Swimming Pools, Spas, Hot Tubs and Other Recreational Water Facilities covers materials, chemicals, components, products, equipment, and systems related to public and residential recreational water facility operation. This scope extends the standard’s applicability beyond just pools.

The NSF/ANSI 50-2021 standard document covers evaluation and testing guidelines for swimming pool treatment chemicals, filters, centrifugal pumps, non-integral strainers, valves, mechanical chemical feeding equipment, filtration media, UV light process equipment, automated controllers, heaters, flow metering devices, and numerous other components integral to the operation of recreational water facilities.

Changes to NSF/ANSI/CAN 50-2021

The 2021 edition of this standard is the most current, and it revises the previous version from 2020. Some major changes made to NSF/ANSI 50-2021 include:

  • Section 28, “Floatation or Sensory Deprivation Systems and Related Equipment,” was added.
  • Language relating to regenerative media filter testing was modified throughout Section 6, “Filters,” and in Section N-2.4, “Filter media cleanability test.”
  • Language regarding automated controller valves was incorporated into Sections 9, “Valves,” and 19.1.
  • Several definitions were added, including one for “residential supplemental disinfection.”
  • Language was added to Section regarding filter media.
  • NSF/ANSI 419 was added as a normative reference, and language regarding ultrafine filtration was incorporated.
  • Language was added regarding sieve analysis methods in Section 13.2.2.
  • Language relating to display resolution was added in Section 24.11, “Display resolution,” and further use instructions were added to Section 24.14, “Installation and operation manual.”
  • The scope of Section 26, “Interactive waterplay venue surfacing systems,” was updated in Section 26.1.
  • An additional testing protocol for UV reactors was added to Section 15.18.2.
  • Sections and from NSF/ANSI CAN 50-2020 were removed, as they contained redundant language already listed in Sections 13.1.3, “Precoat filter media labeling requirements,” and 13.2.5, “Sand and alternate sand-type media labeling requirements.”
  • Language regarding the default media for filter testing was added as Section 6.1.11, “Cryptosporidium parvum oocyst reduction.”
  • Clarified and harmonized language in Sections 14.19 through 14.21, Section 14.23, and Section 15.8.
  • Updated language regarding validation of UV dose displays throughout Section 15, “Ultraviolet (UV) light process equipment.”
  • Updated language regarding UV display validation in Section 15.5.2.
  • Clarified and corrected language in Sections 6.1, 6.1.8, and N-2.4.5.

Changes to NSF/ANSI/CAN 50-2020

The 2020 edition of this standard revised the 2019 version. Some major changes made to NSF/ANSI 50-2020 include:

  • Definition for “high capacity cartridge filter” was added.
  • Language relating to turbidity reduction testing, pump flow rate outputs, and piping materials was updated.
  • Language was added for crypto reduction claims for filters.
  • Language regarding low pressure UV lamp testing was modified.
  • New Section 27, “Treatment chemicals used in recreational water and facilities,” was added. This new section contains some information previously found in Normative Annex 12, “Flow metering devices outdoor use,” and contains clarifications to the scope for pool chemical evaluation.
  • Typos in the chemical evaluation tables were corrected.

Changes to NSF/ANSI/CAN 50-2019

The 2019 edition of this standard, which revised the 2017 version, was substantial. The most noticeable change visible to past users is the addition of the “CAN” designation. In fact, this edition of the standard for swimming pool treatment chemicals and equipment was the first to be designated as a National Standard of Canada (NSC) in compliance with requirements and guidance set out by the Standards Council of Canada (SCC).

Other notable changes made to NSF/ANSI 50-2019 include:

  • Language relating to chlorinator sizing from Annex I-1 (formerly Annex J) was removed.
  • UV Treatment System requirements were clarified.
  • Water quality testing devices accuracy levels were modified.
  • Language regarding shelf life testing of water quality testing devices was adjusted.
  • Units related to UV control panel requirements were corrected.
  • The uniformity of output testing for chemical feeders was updated.
  • Slip resistance testing.
  • Head loss equations were revised.
  • This revision brings consistency and clarity throughout the standard by way of a “clean-up” ballot.
  • Language was revised regarding skimmer requirements.
  • Normative references were moved out of Section 1 into their new Section 2. This marks an editorial adjustment that permeates throughout the entire document, as all other sections were moved up by a section number.

Furthermore, keeping in line with the change we saw with other NSF International standards published in 2019, the annexes in NSF/ANSI 50-2019 were changed from alpha characters to numeric and preceded by “Normative” or “Informative.” For example, Annex A from NSF/ANSI 50-2017 is called “Normative Annex 1 (N-1)” in NSF/ANSI/CAN 50-2019.

Changes to NSF/ANSI 50-2017

NSF/ANSI 50-2017, which was published in 2018, replaced the 2016 version of the same standard.

Much like with the 2019 edition, one of the obvious changes made to the 2017 revision was with the title, as it explicitly included the chemicals related to recreational water facility operation. The scope was also updated to reflect the inclusion of chemicals. Other than this update, NSF/ANSI 50-2017 underwent the following changes:

  • Language for UV disinfection was aligned with that in the 2014 Model Aquatic Health Code (MAHC).
  • Language for shelf life testing for manufacturers of water quality testing devices was revised.
  • The water quality testing devices (WQTD) sections were updated.
  • Flow meter language was revised to reflect consideration of the devices being used in applications where specific gravity is greater than 1.0.
  • Normative references were updated.
  • Specific criteria for metal contaminant limits were added.
  • Language adding clarity to effective size and uniformity coefficient calculations was incorporated.
  • Language regarding chemical feeders was revised.
  • Language regarding formulation testing in Annex A, “Materials review and qualification methods,” was revised.
  • Exposure assumptions were updated in Annex R, “Toxicology review and evaluation procedures for swimming pool treatment chemicals.”

Download NSF/ANSI 50

NSF/ANSI/CAN 50-2021: Equipment and Chemicals for Swimming Pools, Spas, Hot Tubs and Other Recreational Water Facilities is available on the ANSI Webstore.

2 thoughts on “NSF/ANSI 50-2021: Equipment and Chemicals for Swimming Pools
  1. This is a very well written article. I will surely bookmark it and come back to read more of your useful information. Thanks for the impressive post.

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