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Enzymes Use in Spas And Hot Tubs

Author: Alan Schuster

A photo of Alan Schuster

I am a graduate of the City University of New York, with a B.S. Degree in Chemistry. My experience in the Swimming Pool and Hot Tub Industry goes back over forty years.

During this period, I have helped tens of thousands of consumers and dealers solve all weather pool and hot tub water chemistry and water quality problems.

It sounds simple enough. Just add some enzymes, to your spa or hot tub, and everything magically falls into place. It’s just not that simple. They have a place in hot water maintenance, but there are limitations and factors, that must be considered, in order to get the desired end results of crystal-clear and sanitary spa water.

So, what are enzymes?

Enzymes are protein molecules and there are endless numbers of different ones. Our bodies use enzymes, thousands of uniquely different ones, to make chemical reactions happen. In doing so, they act as a catalyst, making specific chemical reactions proceed, with organic molecules, but not actually taking part in the transformation and not being destroyed, in the process. How enzymes, present in saliva, start to convert starches into sugar, is an example of such an organic chemical reaction Tweak the enzyme protein molecule, a bit, and it acts in a different way, with other organic molecules. Fortunately, it is a lot less difficult to maintain a spa, than it is to be part of the driving force, behind a living organism.

When enzymes were first used, they were touted to be a cure-all. Simply add some enzymes and let nature take its course. The same was said of ozone. Just ozonate and nothing else would be needed. In the real world, things are not that simplistic and mother nature is a wary adversary. Enzymes can destroy or decompose organic molecules, but they don’t act that way, when encountering living organisms. Enzymes have to be chosen or developed, so that they do not adversely affect living organisms.

To do otherwise, would expose bathers to irritation and sensitivity reactions. Living organisms are not organic molecules. They are, in fact, the end result of billions of billions of organized organic molecules, following the blueprint of DNA. By comparison, an organic molecule can be miniscule. With this in mind, enzymes are not sanitizers or disinfectants. They don’t kill bacteria, mold, fungus, yeast, single celled microorganisms or anything living in your spa water, pipes or filter. If well chosen, they don’t seem to affect or irritate the bathers and help improve the spa experience.

What do enzymes do in a spa?

They act upon non-living organic matter, starting decomposition into small molecules. The smaller molecules are more easily destroyed by chlorine or bromine. Organic wastes include a wide range of things, such as: sweat, body oils, saliva, mucous, dead skin, cosmetic residues, sunscreens, perfumes, hair, feces, urine, leaves and wind-blown debris. Some of these contaminants are readily destroyed, by normal levels of chlorine, while others may be slow to react or actually deplete the chlorine or bromine level.

Side view of an All Weather Pool

Consider a piece of fecal matter, caught in the filter. If only chlorine or bromine are present, the time to eliminate it completely, might drag on, until all the sanitizer is depleted. If enzymes are present, the enzymatic proteins will go from molecule to molecule, degrading them into smaller molecules, that are more easily and efficiently destroyed by chlorine or bromine. In effect, the enzymes are making the task of sanitizing more effective. More of the chlorine or bromine is available to sanitize and protect against the microorganisms, be they pathogens or non-pathogens, that cannot be killed, by just an enzyme. By helping to degrade organic wastes, of all types, less chlorine or bromine is required to maintain a satisfactory level.

Enzymes cannot eliminate the need for some chlorine or bromine, but they can contribute towards a reduced chemical presence. A spa is purchased for a reason, typically family fun, relaxation or therapy benefits, and better water quality and maintenance results are a worthy and attainable goal.

Organic wastes need to be eliminated, from spa water, the pipes and filter. Chlorine and bromine, help, towards this end, acting as oxidizing agents, as well as sanitizers. As water, containing enzymes, travels through the circulation system, any organic wastes encountered will start undergoing decomposition. 
The more that this decomposition is enzyme-initiated, the more chlorine and bromine will be left available, both to eliminate organics and sanitize.

Not all wastes lead to the same problems. Urine and other nitrogenous organic wastes, for example, deplete the free chlorine level very rapidly and increase the presence of combined chlorine or chloramines, which are odorous, irritating and ineffective as spa sanitizers. That unpleasant odor, sometimes associated with chlorine, is due to chloramines and not simply chlorine. A typical person can detect chloramines at 0.1 PPM, while not sensing chlorine levels under 30 PPM.


The presence of enzymes can help the nitrogen, present in the urine, to gas off. With less organic nitrogen present, chloramine formation is reduced and the chlorine consumption is reduced. An ideal level for combined chlorine is under 0.3 PPM. In order to eliminate 1 PPM of combined chlorine, you have to super-chlorinate the spa, by adding 10 PPM of new free chlorine. This helps achieve break-point chlorination, reducing the chloramines content to a value under 0.3 PPM. This need to shock the spa is not necessarily a convenient thing to do, on a frequent basis. The more enzymes are able to decompose the nitrogenous organic wastes, the less the need to super-chlorinate.

However, occasional shock treatments do help prevent the development of sanitizer-resistant microorganisms. The use of an in-line salt chlorine generator or ultraviolet sterilizer helps destroy chloramines, as water passes through the cells. If you want to reduce the combined chlorine odor, the use of enzymes can be beneficial.

Another example of not all organic wastes being the same are body oils and sunscreens. They tend to be water repellent or hydrophobic. Chlorine and bromine are water soluble and tend to be hydrophilic. The hydrophobic nature of the body oils acts as a shield, against the water, resulting in less contact between wastes and the chlorine and bromine. Enzymes or organic compounds are less likely to be repelled, by the body oils, which will aid in the decomposition of the waste products.

As the body oils are degraded into smaller molecules, chlorine and bromine should be better able to hasten the complete elimination. Some enzymes have special surfactants or wetting agents, added as an ingredient. This tends to make the water wetter and speeds the action of the enzymes, upon the organic wastes. Making water wetter may sound like an alien concept, but this next example illustrates the point. Wax a car to a high shine and sprinkle some water on the hood. The water beads up and is really barely touching the hood, as most of the water is in the drops. Add some detergent (surfactant) to the water and do the same thing. This time the water does not bead up and wets the hood. There is more contact area and this is why a surfactant can make water wetter.

Body oils deserve some special consideration, as they present an additional problem. The foam that develops, as spa water is aerated, is not as innocuous, as it would seem. The foam is caused by the formation of “soaps”, resulting from the reaction of the body oils and the natural alkalinity of the spa water. The aeration causes these “soaps” to start foaming. The US CDC has determined that the microbial populations and the sanitizer levels, of the foam and spa water, are not necessarily the same. The foam is likely to have less sanitizer and support higher levels of microbial growth. While the use of a silicone-based anti-foam can offer a solution, it is temporary, at best.

A woman applies sunscreen on her legs

The only true way of assuring proper sanitation, even with ideal sanitizer levels and water chemistry, is to completely defoam the water, on a regular basis. For a typical residential spa, this usually occurs after the air jets are turned off 

and the water becomes less turbulent. If an enzyme product is in use, it follows that the level of foam
should be reduced, because some of the available body oils were decomposed or degraded. In addition, by degrading the organics, the enzyme should keep more of the chlorine and bromine available, for daily, routine sanitation.

Foam in a spa is not a good thing and should not be confused with a bubble bath.

Spa users and swimmers, in general, prefer to have less of a chemical sensation. Bather comfort necessitates that sanitizer levels and the overall water chemistry be maintained, within prescribed ranges. In a spa, the sanitizer level can quickly deplete, due to the bather versus volume relationship. When a self-replenishing system, such as a salt chlorine generator is in use, a more consistent and predictable sanitizer level can be expected. Enzymes help preserve the chlorine or bromine, for actual sanitizing, so that less chemicals have to be added. The chemical savings are real, but the greater benefits are more efficient sanitation and a better hot water experience.

A case has been made, for why enzymes, used as part of a maintenance program, can improve spa water quality and the bather experience. Organic waste products will be eliminated more efficiently, more chlorine or bromine will be kept available for actual sanitation work. Less chlorine or bromine will be required to maintain any given level, the odors associated with combined chlorine formation will be reduced and super-chlorination treatments will be required less often.

Foaming should become less problematic and the overall bather experience will improve, due to a perceived, reduced chemical presence. Of course, all of these benefits depend on the spa owner or operator doing their part. The more attention paid to sanitizer levels, water chemistry, water circulation, filtration and cleanliness, the greater the likelihood to an improved and enhanced outcome.

You can operate a spa without the use of enzymes, but there are benefits that could be lost. Are those benefits worth the cost? That’s something that is hard to quantify. How much value do you place on better water quality, fewer problems and an improved hot water experience? Simply avoiding one problematic incident could offset the cost of the enzymes. The actual product cost varies considerably, as not all enzymes are the same, in terms of formulation, concentration and effectiveness. When you purchase a chlorine product, the law requires that the active ingredients be disclosed, both in terms of concentration and chemical identification.

It’s easy to make a cost comparison, when you have this type of information. Enzymes are not sanitizers and, as such, are not required to list the ingredients or concentration, on the label. This causes trying to make an informed purchase more difficult. Comparing the cost on a bottle-size by bottle-size basis, does not always tell the whole story. You don’t know the concentration and ingredients.

These are proprietary formulations and there have to be brand to brand differences. Some formulations probably contain surfactants and other ingredients, while others might not or could contain very different amounts. Does the product contain one enzyme or a mixture or several? Do you opt for the larger bottle, that is lower priced or choose the smaller bottle, at a higher price?

Bottles of Arctic Pure chemicals

To further compound matters, enzymes are added in terms of a dose, every so often, as indicated on the label. It’s easy enough to determine the cost of a dose, for any of the available products. However, that doesn’t tell you what is in that dose or how well it will work. With chlorine or bromine, you have something to measure. You have a real-time way of determining the effectiveness of the product. 
Unfortunately, with enzymes there are no tests, that determine their presence or functionality, that are available to a homeowner. In deciding, whether or not to use an enzyme treatment, it becomes a leap 
of faith, as it is something that you can do without. In the final analysis, enzymes do offer the prospect of better results and fewer problems, at an affordable cost. Choosing a brand with a proven track record would be the place to start.

The recommendations of dealers or fellow spa owners should be considered, in making a product selection. Enzymes are not “silver bullets” and the final outcome is dependent, upon how well the addition of an enzyme treatment is integrated into the overall spa maintenance. Do your share and, hopefully, the enzyme will help take your water to the next water quality level, leaving you to better enjoy the spa experience