Why, where and when was this research performed?

eco3spa is a new product and both we, the manufacturer, and potential users need to have confidence that it is safe to use in a hot tub sanitising environment. There is traditionally a great deal of resistance to using any product other than chlorine or bromine to sanitise hot tub water, mainly because it has been felt that sufficient test data has not been available to prove the efficacy of other options.  The prevalent use of Active Oxygen sanitation worldwide during the Covid 19 pandemic has raised its profile as an extremely effective method of sanitation but, prior to this research, there was very little hard data to prove the use of the product in hot tubs.

This research was performed at Swansea University jointly within the faculty of Life Sciences and the faculty of Chemical & Environmental Engineering between October 2019 and April 2023 to specifically look at the performance of the eco3spa products in a hot tub environment.  

The hot tub 'microbe problem'

Hot tubs are regularly kept at temperatures where microbes (or bacteria) like to grow. This is a problem if pathogenic (illness causing) bacteria grow in our hot tubs. Commonly this can cause skin irritation and worse

In domestic hot tubs lack of owner knowledge and inadequate cleaning increases the risk of biofilms forming on hot tub surfaces. This problem is exacerbated by inappropriate use of biofilm control agents which in the long term can promote antimicrobial resistance

How do bacteria grow in hot tubs?

  1. Planktonic bacteria. Also known as free living, waterborne bacteria, these are bacteria growing in the water and not stuck to surfaces.  They are mainly individual bacteria but occassionally clumps occur.
  2. Biofilm.  Biofilm are bacteria growing whilst stuck to a surface
bacterial growth in hot tubs

What were the objectives of this research?

  1. To test the efficacy of the eco3spa Step 3 Sanitiser (Multi-function Active Oxygen Tablets or Granules) as a biocide against prevalent hot tub infectious agents Pseudomonas Aeruginosa and E-coli at a range of concentrations and water pH values, and at water temperatures typically found in hot tubs.
  2. To test the efficacy of the eco3spa Step 3 Sanitiser at preventing Pseudomonas Aeruginosa and E-coli biofilm formation at a range of water pH values and temperatures.
  3. To compare the efficacy of the eco3spa Sanitiser to that of chlorine at a range of temperatures and pH values.
  4. To study the role of the eco3spa Step 2 Water Conditioner in the sanitising process.

How was the research performed?

One domestic hot tub contains about 1500 litres of water and it is very inconvenient to do experiments at this scale!

To make the experimentation possible common laboratory  96-well Microtiter plates were used.  These plates enable many scaled-down variations of an experiment to be performed in parallel.

Each product was dissolved in water at a range of concentrations and a range of pH values to replicate use in a typical 1500 litre hot tub.  E-coli and Pseudomonas Aeruginosa bacteria were exposed to the solutions being tested at two different temperatures (25°C and 37°C) and a range of different pH values.

A substance was added to the microtiter plate which stained the cell neuclei of any live bacteria cells.  The growth of bacteria could then be measured by measuring the optical density of each well in the plate.

independent laboratory research

Short Summary of the Results

  • How well does eco3spa sanitiser work?
  • eco3spa sanitiser benchmarking
  • eco3spa longevity
  • does eco3spa sanitiser work as well as chlorine
  • does eco3spa sanitiser work as well as chlorine on biofilm


eco3spa is a suitable and safe alternative to chlorine for domestic hot tub use

Independent university research has shown that the product is highly effective at maintaining safe, healthy hot tub water.

eco3spa works at a much broader pH range than chlorine or bromine, meaning there is no need to adjust the pH of the water and overall chemical usage is significantly reduced.

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