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Good Chemistry

200501JF0Water is a chemical compound with a variety of physical characteristics, including the ability to act as a solvent and to harbor life.  For those two reasons alone, says chemistry expert Jeff Freeman, watershape designers and builders should want to know everything they can about water chemistry –  but they typically don’t.  Here, he begins a new series on the importance of water chemistry with a discussion of why watershapers really do need to care.

  By Jeff Freeman

Plainly stated, water has chemical characteristics that affect the longevity of a watershape and the near- and long-term ability of our clients to enjoy their experiences in and around the water.

For all the clarity and obviousness of that assertion, however, there’s a marked tendency among watershape designers, engineers and builders to assume that maintenance of proper water chemistry is the exclusive responsibility of service providers who come onto the scene once our work on a project is done.  

As watershapers, we build beautiful projects that become a huge part of our clients’ lives.  Almost invariably, they’ve spent a significant amount to enhance their lifestyles and enjoyment of their homes.  Just as most of us wouldn’t dream of building a pool, spa, fountain, stream or pond or accepting payment without installing some sort of a pump and filtration system, I’d argue that we should never create systems that don’t anticipate and accommodate the need to maintain proper water chemistry.

This series of articles will back up that assertion with a detailed look at various aspects of water chemistry and the effects they have on the products and materials we use as watershape designers and builders.  After a basic overview in this installment, we’ll systematically look at what we can do to make sure that the quality of the water never becomes a detriment to the beauty and pleasure we all strive to deliver.   


A big part of doing our best for our clients involves taking all of the elements of water treatment into account while we are designing and building our projects.

That includes allowances for proper filtration, circulation and skimming, which play key roles in good water quality and which we all seem to know we must consider.  Less well recognized is the fact that it also includes the need to plan for and provide the means to treat the water itself.

For starters, proper sanitizing makes a body of water both safe and aesthetically pleasing.  You don’t need to be a microbiologist these days to know that there are a variety of waterborne diseases that can assault bathers if things aren’t right.  And even if the water isn’t unsafe per se, inadequate sanitizing can leave water cloudy, malodorous and riddled with algae.

At the same time, water balance (which I’ll explain in greater detail below and in upcoming articles) is absolutely essential to protecting plaster, tile grout, exposed aggregates and faux and real rock from scaling, staining, etching or generally falling to pieces.  In addition, proper chemistry also helps protect the durable performance for all the components on the equipment pad.

The trouble is, of course, that not all contained, controlled bodies of water are created equal, which means there are significant differences in treatment approaches that come into play.    

In the case of swimming pools and spas and fountains, for example, the need for good chemistry is critical because people immerse their bodies in the water and will avoid water that is either murky or has an unpleasant smell.  (Yes, that’s even true with fountains because there’s always the possibility that someone will jump in and swim around from time to time.)

On the opposite side of the scale are systems that harbor plants and fish:  Here, the water-chemistry challenge requires a completely different approach – no less rigorous or important, just different.

In all cases, be it sanitizing water to keep it free of algae and harmful microorganisms or maintaining its balance to keep it from attacking cementitious materials, the designer and builder have a variety of options.  The key to success, no matter the regimen you choose, is that water chemistry cannot and should not be left to chance.


As designers, engineers and builders of various types of watershapes, we need right up front to recognize a reciprocal relationship between water chemistry and the materials we use in our projects.

Water chemistry, for example, affects the longevity and service lives of the materials with which watershapes are surfaced, and the types of materials you choose will in turn have an effect on chemistry.  Plaster, natural rock, artificial rock and tile grout, for example, can all be attacked by aggressive, mineral-seeking water – or stained or coated with scale when water slides out of balance the other way.

The Chlorine Scene

Chlorine is an atomic element that belongs to the halogen family.  In nature, it is found in various chemical compounds, primarily bound up in seawater in the form of sodium chloride, or salt.  For decades, scientists and chemical manufacturers have figured out ways to add chlorine to water as a sanitizer by combining it with other chemical compounds.

Regardless of how it’s added, chlorine possesses several characteristics that are important to water treatment.  First, it dissolves easily in water and its levels (that is, its residuals) are easily monitored using either chemical reagent tests or electronic monitors.  

In all cases, chlorine is used up by bacteria and organic compounds introduced by bathers, dirt, pollen, leaves and animals, to name a few sources.  The more of these entities that find their way into the water relative to the size of the body of water, the more sanitizer the system will require.

All chlorine compounds have an influence on pH and water balance.  Chlorine is also both a sanitizer, meaning it kills germs, and an oxidizer, which means it burns up organic compounds that can lead to the formation microorganisms or algae.  We’ll explore these functions more fully in future articles.  For now, let’s run through basic product forms used in watershapes.

[ ]  Sodium hypochlorite:  The most commonly used and most familiar form of chlorine is sodium hypochlorite, or liquid bleach – pretty much the same stuff used in laundry rooms.  Sodium hypochlorite is added to water either by hand, as in the “bottle at the end of the arm” method, or more reliably by a chemical feeder of some type or a salt-chlorination system.  

[ ]  Calcium hypochlorite:  This is a granular chlorine that is also widely available and can be added by hand or a chemical feeder of some kind.  Like sodium hypochlorite, it is both popular and very affordable, but “cal hypo,” as it’s often called, is highly volatile and must be handled with due care.

[ ]  Chlorine tablets:  These are the familiar white tablets known commonly as trichlor and contain chlorine as well as cyanuric acid, a chlorine-stabilizing substance.  (See the sidebar on page XX for more on chlorine stabilization.)  In addition to being used in chlorine floaters – a tremendously flawed delivery system – trichlor is commonly added to water in a type of flow through, in-line device known as an erosion feeder.

[ ]  Chlorine gas:  Also known as “elemental chlorine,” this is another means of adding chlorine to water.  As its name suggests, chlorine gas is pure chlorine with no additives and must be added to water using special injection systems – generally by a service specialist who uses a device known as a diffuser to add the chemical to the water.  Chlorine gas is extremely toxic and can cause significant injury if inhaled, but it is also an extremely cost-effective and reliable means of sanitizing the water.

There are other options as well, including sodium dichlor (a granular form similar to trichlor) and lithium hypochlorite (similar in some ways to calcium hypochlorite, but with a more neutral pH).

-- J.F.
As a rule, the more cementitious compounds you place in contact with water, the more likely it is that those compounds will be sought by the water to the eventual detriment of the surface as well as to the stability of the pH and performance of the sanitizer.  (How well the cementitious materials are sealed will have a tremendous influence on the effective aggressiveness of the water and, conversely, on the performance of the sealer.)

It’s also true that the size of the body of water relative to its usage is a big factor in water treatment.  Spas, for example, are relatively small bodies of water that are sometimes occupied by relatively large numbers of people.  This means that chemical treatment for spas must accommodate the need for rapid replacement of sanitizers, while fountains may experience the presence of bathers only rarely and may only need a sanitizer level that will head off the development of algae – a different management issue altogether.

The choices among treatment approaches, however, are not always so cut and dry.  And it’s not helped by the fact that, in the world of water chemistry, we are inundated by information put forth by people who may be shooting from the hip, may not fully understand the issues or are spreading partially true or even untrue information based on a need to market a product or system.

In a world where it’s tough to know whom to believe, it’s too easy to fall in behind those with simple approaches who isolate one variable or another, treat that variable and then grossly over-generalize the way things actually work.

In truth, every aspect of water chemistry is tangled up with every other aspect.  Chlorine levels, for example, have an effect on the pH of the pool, which in turn influences the effectiveness of the chlorine.  For their part, algaecides work well in stemming the tide of a current outbreak, but the problem almost invariably returns and requires even more intrusive approaches.  (It’s like an addiction:  A watershape develops a dependency on certain types of water treatment, and the clients find themselves on a frustrating and expensive treadmill.)


To begin to grasp the topic in all its complexity, it’s useful to break chemistry down into the two key areas mentioned above:  sanitizing and water balance.

At root, sanitizing the water is all about providing a means for killing enough harmful microorganisms – or pathogens, as biologists call them – to render the water safe for human consumption.  (By contrast, sterilization is about killing everything in the water.)  In the pool/spa industry, the standards for sanitizing are based on the presumption that the water must be safe to drink, as defined by National Sanitation Foundation (NSF) Article 53.

Chlorine Alternatives

For all of its popularity and widespread use, chlorine is not perfect for watershape applications.  Concerns over its effects on water balance, its often-corrosive nature and its overall toxicity have led scientists and suppliers to develop a host of alternative products and systems.

[ ]  Bromine:  This is another element from the halogen family that is often used in pools and, especially, spas.  Bromine comes in both granular and tablet forms and is an extremely effective sanitizer, but it cannot be stabilized to resist degradation from sunlight and hence is most often used in indoor settings.

[ ]  Biguanides:  By comparison to chlorine and bromine, this is a relatively new form of sanitizer and is based on modern polymer chemistry.  Biguanide sanitizers can be added by hand or by a chemical feeder and are considered to be “gentle” sanitizers because they are not corrosive, as are the halogens.  The product is good at killing pathogens, but it’s not an effective oxidizer, which means it must be used in conjunction with a separate oxidizer, such as hydrogen peroxide.

[ ]  Ozone: A form of oxygen, ozone is an incredibly effective sanitizer and oxidizer when added to water by way of an ozone generator that transforms oxygen to ozone using one of two basic methods:  corona discharge, which emulates chemical reactions in electrical storms that produce large amounts of ozone, or ultraviolet light systems, which generate ozone as well.  Highly unstable, ozone lasts for minutes (or even seconds) when dissolved in water, which means that it has to be injected constantly and should always be used in conjunction with a secondary sanitizer in pool or spa applications.

This is an expensive alternative, particularly in the corona-discharge format, but it is very effective in treating bodies of water that cannot contain chlorine for one reason or another, as in the case of marine exhibits where fish and other aquatic life forms will die in the presence of chlorine or bromine at levels that are higher than those encountered in their natural habitats.  

[ ]  Ultraviolet light:  A completely different approach to sanitizing involves exposing water to intense ultraviolet light (as compared to the less-direct approach of using UV light to generate ozone).  This method kills germs but cannot oxidize organic compounds and so has become a popular option in natural bodies of water that contain plants and fish.

There’s a tremendous amount of specific information about the chemical characteristics of these options, and each may eventually get an article of its own.   

-- J.F.

That standard does not necessarily apply to fountains, depending upon the specific application, nor is it relevant for ponds and streams that contain life.  For purposes of this discussion, however, we’ll set aside biological systems and assume that our watershapes of all types are made with the idea that, at some point or other, a person will take a dip in the water and likely will drink some of it.

It should come as little surprise in this context that chlorine is the most popular sanitizing chemical.  It really is amazing stuff – omnipresent in industrial manufacturing processes, plastics and petrochemical products in addition to being a tremendously effective sanitizer in water-treatment and other applications.  (The sidebars above and at right introduce the various forms of chlorine-based and non-chlorine sanitizers now available.)    

For its part, balancing the water is about accommodating key chemical characteristics of the water and keeping them at levels that ease the process of maintaining a functioning, healthy watershape.

Sounds simple, but it’s not.  We’ve all heard water referred to as “the universal solvent,” meaning that over a given period of time, water will dissolve almost anything.  More to the point, water contains mineral constituents that will render it either acidic or basic – a factor that changes either rapidly or slowly depending upon how the water is managed.

In general, acidic water lacks those mineral constituents and will readily corrode or dissolve an array of materials including cementitious pool surfaces and copper heat exchangers.  In other words, corrosive action is the water’s way of finding compounds it needs to reach a proper balance on its own.

Basic water is just the opposite:  It carries an excess of chemical compounds and will release some of those materials in the form of mineral deposits, scale or stains – and it, too, can be corrosive.  Basic water is, therefore, quite as capable as acidic water when it comes to damaging interior surfaces, plumbing and equipment.  


The basicity or acidity of the water is measured in pH, the so-called “power of hydrogen,” which is expressed by way of a logarithmic scale from 0 to 14.  The lower the number, the more acidic the water; the higher the number, the more basic.  The magic digit in terms of pH balance is 7, which means that the water is neither basic nor acidic.

Sounds simple, but again it’s not.  Water’s pH is influenced by a number of factors, chiefly total alkalinity and calcium hardness, which in turn influence each other as well as pH.  As a general rule, however, the higher the levels of total alkalinity and calcium hardness, the higher the pH – and vice versa.  But that’s a hazardous oversimplification, because there are many possible permutations of these three factors that can lead to wide range of balance conditions.

Chlorine Stabilization

As mentioned in the accompanying text, some forms of chlorine contain what is known as a stabilizer, cyanuric acid.  This combination was developed to protect chlorine from ultraviolet-light degradation, which happens very rapidly when the sun shines on the water.  This can quickly make a watershape unsafe because of a depleted sanitizer level, and it can be costly to try to keep up with the demand.

Cyanuric acid is added to the water one of two ways, either as part of the chlorine compound (as with trichlor or dichlor) or separately (as when liquid bleach, calcium hypochlorite or chlorine gas are used).

The other major halogen sanitizer, bromine, does not at this time have a chemical mate that can stabilize it in the presence of sunlight, which is why bromine is most often used with indoor bodies of water or in those that will remain covered much of the time – as with a spa with some form of thermal cover.

-- J.F.

Also influencing pH is the water’s level of total dissolved solids – that is, the sum total of everything that is dissolved in the water – and the levels of different sanitizers, each of which has its own pH value and influence.  And then there’s the fact that pH influences how well sanitizers work and for how long.  

In other words, managing both sanitizing and balance – and doing it constantly, simultaneously and efficiently – is the key to success.

Water balance is itself maintained through the addition of chemicals, either an acid of some kind to push the balance in an acidic direction or some sort of buffering agent to make the water more basic.  As with sanitizers, there are automated chemical-feeding systems that can be deployed to monitor and adjust all of these key chemical levels.

To be sure, ongoing maintenance of sanitizer levels and water balance will largely be the domain of whomever it is who services a given body of water.  Nonetheless, the choices that designers and builders make at the outset of a project have tremendous influence on what that maintenance process ultimately will be.

For example, the designer who specifies use of monitoring and chemical-feeding systems will take a long-term role not only in the approach subsequently used in maintaining the water, but will also to certain extent dictate the types of chemicals used to sanitize and balance the water.


One more key point:  Every watershaper faces the moment when he or she fills the watershape – the most important drink of water the system will ever take.  That’s so because fill water comes with its own set of chemical characteristics (particularly with respect to balance) and must be treated before or immediately after it is introduced to the watershape.

In the pool/spa industry, this event is known as the “start up,” and there are various ways in which it can be accomplished and fiery disputations about which method is best.  One thing is certain:  The way you introduce the water to the watershape will have a tremendous influence on the longevity of the system and especially on the completion of the curing processes for plaster, concrete and grout.

We’ll jump into these areas in detail in upcoming articles.  For now, the main point with which I’ll leave you is this:  Water chemistry is not nor has it ever been the sole province of service and maintenance people, but is also a way for the designer and/or builder to set the stage for the way the water will be treated later on.  To push the responsibility down the chain is, as we shall see, both risky and potentially quite costly.


Jeff Freeman is director of technical services and commercial sales for Balboa Instruments of Tustin, Calif., and is also founder of Fluid Logic, an independent hydraulics-consulting firm in Upland, Calif., that specializes in complex aquatic systems.  He entered the watershaping industry more than 20 years ago, working for a wholesale distribution firm. He later established his own service and repair company, then returned to the distribution business as a product representative working with swimming pool and spa builders. He has extensive experience designing and troubleshooting hydraulic systems and has taught the subject at the California Polytechnical University in Pomona, Calif.

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