Water Care Basics to Prevent Biofilm Formation

The organic matter introduced into the water by two bathers during a 20-minute soak can eliminate almost all traces of available sanitizer.

After many years working in the water chemistry field, this author still gets the same question: What is the most important aspect of hot tub water care? In speaking to hot tub customers, service technicians, water care sales teams, retailers, and store owners from all over the world, the answer remains the same: The best way to enjoy the hot tub experience is to maintain the proper sanitizer levels in the water and prevent or remove biofilm buildup in places like plumbing lines, shell surface, or filters. These are the two pillars to hot tub maintenance.

Understanding why sanitizing and controlling biofilm are important

When using chlorine as a sanitizer in the hot tub, it is recommended the water should always maintain a residual of 3 to 5 parts per million (ppm), or 4 to 6 ppm when using bromine. Basic test strips reflect this benchmark with the acceptable color region used to indicate water chemistry levels. It is necessary to monitor and regulate these levels daily.

Hot tub water must always have the recommended level of sanitizer available to keep the water free of harmful bacteria. Why is this important? Consider the following: The organic matter introduced into the water by two bathers during a 20-minute soak can eliminate almost all traces of available sanitizer. There is no sanitizer remaining because it has performed its job of destroying the organic particles introduced into the water by the bathers. This is why the addition of a sanitizer should mirror hot tub usage.

There are simple ways to achieve a consistent sanitizer level. Chlorine and bromine are the most effective chemicals to reduce or kill bacteria in hot tub water. A chlorine generator will convert salt to chlorine, while an ozone system also works well to support sanitization. Floating dispensers, filters, in-line plumbing sticks, granules, liquids, or tablets are all ways of introducing sanitizer into the water.

A low/inadequate sanitizer level is a direct link to many problems relating to the inability to achieve clean and clear hot tub water. For example, one common issue is cloudy, odorous water. Shocking the water with a sanitizer can easily solve this problem.

In other cases, the water can be so far out of accepted balance that bacteria will proliferate to the point where super chlorination is necessary. This requires keeping the hot tub water above 10 ppm free chlorine for 24 hours. Super chlorinating can resolve the issue and eliminate the need to drain and refill the hot tub; however, it does not need to reach this point.

Adding a non-chlorine shock oxidizer after each hot tub use is another preventative measure that helps sanitizers work more efficiently, while also providing a more luxurious and relaxing hot tub experience. In fact, dispensing 28 to 56 g (1 to 2 oz) of potassium peroxymonosulfate (also known as MPS, and potassium monopersulfate) non-chlorine shock will oxidize organic matter quickly. This will help keep the hot tub water clear for longer periods, while also improving the sanitizer’s efficiency.

Some common complaints from hot tub owners are the way sanitizers smell or that they are harsh and dry out their skin. In these cases, the use of a water conditioner can help or completely neutralize the negative side effects of chlorine or bromine.

Hot tub owners should think of routine hot tub water care in similar fashion to washing and conditioning their hair. For instance, shampoo cleans the hair, which is the equivalent to sanitizing the water, while conditioner makes the hair healthy, shiny, easy to manage, and stronger for the future, which is similar to conditioning the water to make it softer and fresher, while also protecting hot tub components from the harsh cleansing.

Preventing and removing biofilm to protect bathers

Ideally, maintaining chlorine levels at 3 to 5 ppm or bromine levels at 4 to 6 ppm will effectively prevent the formation of biofilm. Unfortunately, not every hot tub owner stays on top of his or her chemical routine, allowing biofilm to quickly form.

Biofilm is a pre-existing collection of bacteria, microbes, and cells that are surrounded by an impenetrable protective layer. Once there is a biofilm buildup, chlorine or bromine cannot effectively kill bacteria within the biofilm matrix. Biofilm forms a plastic-like substance called extracellular polysaccharides (EPS) that acts like a protective slime layer allowing a collection of bacteria and microbes to form a matrix, and begin colonizing.

It only takes a short period for bacteria to multiply rapidly in poorly sanitized hot tub water. Once a biofilm colony forms, a routine sanitizer treatment program will continue to kill bacteria; however, it will not eradicate the bacteria protected within the biofilm layer. The minute hot tub water does not have an adequate sanitizer level, biofilm takes advantage of this opportunity and the bacteria quickly mobilize to form a protective colony.

The more biofilm builds up in the hot tub water, the more the sanitizer tries to fight the gunk in plumbing, rather than working to keep the water clear and healthy. Biofilm will always have a safe breeding ground no matter the amount of sanitizer present in the hot tub water.

The biofilm formation process

It is important to understand how biofilm forms. Organic matter such as sweat, bacteria, cosmetics, and body secretions will lead to the formation of slimy deposits if they are not destroyed by sanitizers. Even when the water is treated with chlorine or bromine, these deposits remain in the water, settling and sticking to the nearest surface and act as a food source for viable bacteria.

Suspended particles, organic matter, and viable microbes in hot tub water are normally positively charged and can associate and form cumulative aggregate or settle onto surfaces (e.g. inside plumbing) where water is slow moving or stagnant.

Once the initial colonization has started, viable bacteria will quickly begin the process of biofilm construction. Bacteria will enter and exit the biofilm cell matrix. They settle, forming colonies and cell matrices easily. The surface also is normally positively charged, but there is no significant charge repulsion; therefore, they associate naturally.

Quite simply, the only options available for combating these slimy deposits found in the crevasses of hot tubs are to prevent or purge.

Preventing biofilm

Some water conditioners will work to prevent the proliferation of biofilm. The combination of ingredients can suspend organic particles circulating in the water, including microbes. While in suspension, they do not associate to any degree. At the same time, the conditioners have similar effects on clean surfaces, preventing the deposition and association of bacteria and organic debris.

If microbes cannot associate, they are less able to begin biofilm construction. While water conditioners do not destroy, kill, or remove biofilm, they can help to prevent its formation. Water conditioners also have a buffering capacity that assist sanitizers in the water to allow them to function optimally, which further reduces the number of viable microbes that can lead to biofilm formation.

Other water conditioners promote the suspension of floating organics so they do not settle. They flow with the water to the filter where they will be trapped and removed once the filter is rinsed during routine hot tub maintenance.

Removing biofilm

If proper sanitizer levels in a hot tub are inadequate, it is highly likely that biofilm is present. At this stage, the hot tub should be flushed out using a plumbing line purge product. In fact, this regimen should be followed every time a hot tub is drained and refilled.

The belief of pouring copious amounts of liquid or granular chlorine into the hot tub and running the jets on high will do the trick is not effective and will not kill all of the bacteria. This practice will not completely clear the lines of organic buildup.

The proper way to remove biofilm buildup from the hot tub’s plumbing is to use a product that combines surfactants and scouring agents that foam and thoroughly cleanse the piping and tubing throughout the cavity beneath the hot tub. These cleaners degrade the polysaccharides, exposing the contents the surfactant then suspends.

If the hot tub has been in use for many months, a plumbing cleaner can be used for a fresh start. This will dislodge chunks of black, green, or dark-colored matter that will come out of the jets. After completing this process, the hot tub should be drained as planned—only this time it will be free of biofilm.

The root cause

When working in his test centre in Vancouver, B.C., this author routinely examines many manufacturer and product claims and how various chemicals interact to solve water care issues in the hot tub industry. According to this author’s findings, the lack of basic routine hot tub water care is typically the origin of many consumer problems.

Many owners find hot tub upkeep and water maintenance to be challenging, and they certainly do not want to play the role of part-time chemists at home; however, it does not have to be a laborious or tedious process. Owners who sanitize regularly and purge with a plumbing cleaner during every drain and refill will not only make their hot tub easier to maintain, but also ensure their water is clean and safe from harmful bacteria. In turn, this allows them to enjoy their hot tub and take advantage of all the health and wellness benefits it has to offer.

This article was written by Colin Taylor, B.Sc., MIScT and originally appeared on Pool & Spa Marketing [link].