Effective Or Inadequate?

Many states have only general aquatic guidelines, but those that have detailed, comprehensive pool codes, such as Florida and Nevada, along with the most in-depth service technician/operator certification programs, emphasize the importance of proper filtration and circulation.

Putting bather safety under the microscope. © Can Stock Photo Inc. / Forgiss / Nicemonkey

Along with sanitation regulations, user, structural, electrical safety requirements, circulation and filtration are also a key focus, yet by all indications, there is an oversight in the aquatic industry, and the Center For Disease Control (CDC), based on its published proposed modules, is poised in its Model Aquatic Health Code (MAHC) to be equally remiss in providing for bather health.

It is mind-boggling that only half of the states even require a pool operator to receive formal training and certification by an authorized industry organization, such as the National Swimming Pool Foundation (NSPF) or Association of Pool and Spa Professions (APSP).

At best, the codes include minimum turnover rates, almost universally requiring at least one turnover every four hours for public pools (cf. Southern Nevada Pool Code, section 610.10 Filtering and Circulation), or six per every 24 hours.

They include maximum velocity rates, often not to exceed 10 feet per second (cf. Florida Administrative Code (FAC), Chapter 64E-9.007 (10) Public Swimming Pools and Bathing Places, Recirculation and Treatment System Requirements).

Some require a “portable or plumbed-in vacuum-cleaning system” (FAC, supra, subsection 12). However, nowhere are there any regulations or even guidelines that require:


  • Minimum or even continuous filter flow rates
  • Minimum filtering porosity (the size of the holes in a filter element)
  • Specifics in regards to vacuum-cleaning systems.

Without these requirements, bathers are subject to exposure from virtually all pathogens (disease-causing organisms) not removed by sanitation, which by itself is inadequate.

In addition, the prescribed turnover rates are misleading. They imply that every four hours for a public pool and varying other time periods for other types of pools and spas, the entire volume of the pool is required to be filtered.

As discussed below, the historic Gage and Bidwell Law of Dilution, dating to 1926, debunked that myth. Turnover actually is a quantitative, not qualitative standard.

Slipping Through The Cracks

It is estimated by industry sources and these programs that the great majority of all commercial (and in most cases, public) pools use high-rate sand filters, with a porosity of 20 to 50 microns.

Standard guidelines for dealing with harmful bacteria are lacking. Photo Courtesy of Kenn W. Kiser

There is a growing trend toward using diatomaceous earth (D.E.) filters with porosities below 5 microns, but they are expensive to purchase and maintain.  Older public pools most often use high-rate filters or the less-efficient predecessor, rapid-rate sand filters.

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