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The ugly grasp of biofilms

Establishing health guidelines

The five stages of biofilm development
  1. Attachment: Bacteria attaches to the surface. It wants a place to call home and grow. Bacteria want to be in relationships, so they find a nice surface to settle down and join up with a few of their closest friends.
  2. Colonization: Takes place as bacteria multiply and divide, growing in number. It is at this crucial point this attachment is ‘irreversible.’ The bacteria colony is there to stay unless purposefully removed. This stage is typically accomplished in a matter of minutes or hours at most.
  3. Protection: The bacteria colony or biofilm begins protecting itself against invasion from ‘lethal’ chemicals (e.g. chlorine or bromine), predators, or anything that wants to destroy it. In doing this, bacteria begin to excrete a protective coating called an ‘exopolysaccharide’ film. This film is sticky or slimy, and very hearty. Now the biofilm is ready to experience explosive growth.
  4. Growth: The biofilm gets bigger and tougher. Super colonies of biofilm are actually absorbing certain chemicals that were meant to destroy them.
  5. Distribution: Broken parts begin to attach to other surfaces or different parts of the same surface and the cycle begins anew.Figure_2_redraw

The results of the Texas A&M University study has prompted the Public Health Laboratory Service Water Committee in the U.K. to investigate the link between the use of whirlpool bathtubs and infections further so health guidelines can be established. Likewise, the Dutch government has launched a plan to combat Legionnaires’ disease 
by implementing water safety measures after 242 cases of the disease occurred in 1999 due to the exposure to aerosolized bacteria from a whirlpool spa at the Westfriese Flower Exhibition in the Netherlands.

Due to the presence of pathogenic and potentially pathogenic organisms, public education on the hazards of piped whirlpool bathtub use should become a priority. Immunocompromised and post-operative individuals should discontinue use, and all individuals should avoid submersion of the head and possible ingestion of the water. Another concern, particularly in the hospital setting, is a whirlpool bathtub could act as a reservoir of antibiotic resistant micro-organisms. Exploration of potential preventative measures against whirlpool bathtub acquired infections should be a main focus regardless of the apparent lack of clinical evidence. New technology in design and the use of professional cleaning systems would be beneficial in reducing the risks associated with whirlpool bathtub microbial exposure.

What does this mean for hot tubs?

In this author’s opinion, due to the warm water within the plumbing lines, spa/hot tubs may in fact contain more bacteria and biofilm than a whirlpool bathtub. In this author’s 35 years in the hot tub industry, biofilm was not known as a main contributor of bacteria in water systems. Biofilm has been around forever, but it is not visible as it is hidden in pipelines and equipment. Sure, bacteria are introduced by bathers, but biofilm continues to reproduce as it clings to the pipelines like glue. Biofilm acts as a sheet of armour shielding bacteria from chemicals, allowing it to continue to colonize, breakout, and release into the body of water. This is why many hot tub owners find they have to constantly add more chemicals to sanitize the water even though they have not been using it very often. Even shocking the water with high doses of chlorine (which is bad for bather health and the environment) does not penetrate the biofilm wall and kill 
the bacteria.

By Health Canada standards there needs to be a sanitizer present to kill harmful bacteria, but what about the harmful chemicals left behind? It becomes an ‘if this, than this’ scenario. For example, if there is one part per million (ppm) of chlorine, than the water has no bacteria, which seems to be the lesser of two evils. It is great for killing bacteria, but it makes more sense to be able to obtain the same sanitation level while using less chlorine.

Test kits will measure the quality of water only from where the sample was taken in the hot tub, but bacteria is continually being fed into the hot tub through the jets from the plumbing. If one were to insert a blade into the pipes, scrape off some biofilm and add it to the water sample, the result would be different. Continuing to treat just the visible body of water is no longer the answer; one must remedy the root of the problem. This means removing biofilm so chemicals can attack the freed bacteria in a much more efficient manner.

Historically, there have been products on the market to clean hot tubs, but they only clean part way. Research has found most of them are ineffective in removing biofilm and may only remove some scale buildup. Other products have come along that focus on biofilm and water maintenance, but they are packaged with other products and chemicals making them too expensive for consumers.

Removing biofilm and reducing chemicals is an environmentally responsible move, which will also reduce health risks. If a product is too expensive, the consumer may shy away from it not ever knowing the real value it presents. Another problem may be converting customers to newer, better products as it can be time consuming and, therefore, easier to stick with the ‘if it is not broke, do not fix it’ approach. However, savvy retailers will have the foresight to understand that keeping customers happy is the number one goal. This is especially important for retailers looking to beat their competition by being the first or only retailer with a proven product in addition to having knowledge on water care. Customers need to be presented with the facts and solutions and they appreciate a supplier who is able to offer both.


Moyes, Rita B., “Microbial Loads in Whirlpool Bathtubs An Emerging Health Risk,” Department of Biology, Texas A&M University, College Station, Texas

Williams_HeadshotTed Williams is president of 
Elm Sales & Equipment Inc., 
in Mississauga, Ont. Since 1980, he has been involved in all facets of the Canadian hot tub industry, including wooden and acrylic hot tub manufacturing and design, electro-mechanical and electronic controls design, manufacturing, and distribution.
 He can be reached via e-mail at

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One comment on “The ugly grasp of biofilms”

  1. Got slime or flakes in the plumbing?

    Fixing bio-film in a (portable) hot tub:

    1. Raise hot tub temperature to 104 degrees
    2. Move all diverters to middle position so all the plumbing has water flow
    3. Open every single jet to ensure all plumbing gets flushed
    4. Turn on water features such as waterfalls
    5. Leave the cartridge filters in the tub!
    6. Add 2 to 4 pods of electric dishwasher detergent (I use Costco Kirkland brand)
    7. Run detergent solution through tub at least 24 hours
    a. Turn on high-speed jets several times for at least 20 minutes to scrub bio-film from insides of plumbing
    b. Drain and rinse to sanitary sewer
    c. Remove, clean and rinse filter cartridge(s)
    ***Allow filter to dry completely or install clean/dry backup filter cartridge(s)***
    7. Refill, balance and shock
    a. Keep Chlorine at 3 – 5 ppm for first 24 hours
    b. Turn on high speed jets several times during first 24 hours to flush/sanitize plumbing

    PREVENT BIOFILM: Keep all the plumbing flushed with fresh water and sanitizer
    1. Avoid completely closing jets (especially neck/shoulder jets above the waterline)
    2. Avoid completely turning off water features such as waterfalls.
    (You can turn them down but always leave a little water flow so the plumbing is always flushed with sanitizer)
    3. Whenever adding chemistry or at least once a week:
    a. Move diverter valves to the middle position
    b. Open all jets, turn on all water features to flush all the plumbing
    c. Run jets in high speed for at least 20 minutes after adding chemistry especially sanitizer

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