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Pool Water Basics

It is no secret that pool water requires maintenance. When a technician is at your home diagnosing a problem, you will often hear them refer to pool water that is “out of balance.” I think conceptually we all have a basic idea of what that might mean, but what does it really mean? And what are the implications for pool water that is described as out of balance? In this article, we’ll attempt to provide a basic overview of what balanced pool water is, and some of the symptoms and effects of unbalanced pool water chemistry. Grab your flip-flops and your test kit, and let’s get into it.

The Nature Of Water

If you’ve heard it once, you’ve heard it a thousand times: water is the universal solvent. It is one of those phrases that is used to death by the pool industry because it is such an easily understood analogy to be utilized as a starting point when attempting to educate someone about what balanced pool water is, and how it is achieved. As much as I like the “universal solvent” analogy, I think a more appropriate, albeit less catchy descriptor may be “ a chemical balance pendulum.” I’ll attempt to explain what I mean.

Water is not a benevolent element sitting inactive in your pool waiting to be balanced by the steady hand and watchful eye of your pool service. Water craves chemical balance, and when left to its own devices, it will seek out that balance indiscriminately from whatever resources are available in its environment. For the purposes of this article, that environment is your swimming pool, the materials it is constructed of, and the equipment that runs it.

If we were to take straight, pure water containing no dissolved solids and fill a swimming pool or spa with it, that water would be extraordinarily aggressive; pulling elemental material from the metallic and cementitious components of your pool equipment and structure into solution (aka dissolving it) until equilibrium was achieved. As you can well imagine, this seeking of balance could have quite a deleterious effect on your pool and pool equipment if left unattended. On the flip side of that scenario, water that contains an excessive amount of dissolved material will drop the excess out of the solution (again, seeking balance) in the form of calcium carbonate, or “scale” to use a common pool industry term. This scale may not be acidic in nature, dissolving holes into your pool light ring and pitting your plaster, but it is no less destructive in its own right. Calcified tile and stone, occlusion of your heaters copper heat exchanger, damage to your salt chlorine generator electrodes, and circulation system flow restrictions are just some problems that can be related to “hard” pool water.

Properly balanced pool water not only promotes a healthy environment for your pool's construction materials and equipment, but it is also conducive to a more effective sanitation process and thusly, promotes a healthy environment for you and your family. Although pool water chemistry can be about as complex as you want to make it, there are five major factors that we typically focus on in the pursuit of a chemically balanced pool. Those factors are pH, total alkalinity or TA, calcium hardness or CH, temperature, and total dissolved solids, or TDS. Temperature and total dissolved solids are somewhat secondary to this conversation. We’ll save those two factors for another article. Let's go through the other three of these aspects one at a time and discuss the ideal range for each, what symptoms we can expect from an out-of-balance condition, and some basics on addressing them if they do fall out of the desired range.

pH - ideal range: 7.4 to 7.6

This is the big one. The proverbial star of the show with regard to your pool waters chemistry and the biggest player in our quest to maintain perfect balance. Keep your pH in balance and the remaining factors will be much easier to keep in check. Without a proper pH, all hope is lost. Okay, not really, but without proper pH, you will chase your tail endlessly trying to balance out your water getting nowhere fast but frustrated. Not to mention in its most extreme cases, pH that is not within a proper range can cause major damage to your pool equipment components and your pool finish materials, so let’s keep it in check.

Without getting too technical and bland, pH operates on a scale of 0 to 14. On this scale 7 is neutral. Anything below 7 is acidic, therefore corrosive, and anything above 7 is basic or alkaline and therefore scale forming. As noted in the heading the ideal pH range for your pool is 7.4 - 7.6 which is just slightly basic. This slightly alkaline condition provides a more comfortable swim experience for the user (the pH of the human eye is 7.5) as well as a non-corrosive condition for the pool and equipment. At this point you may be thinking “ I thought the scale was a bad thing, why don’t we want our pH at 7?” If you are thinking this you have a good point, the excessive scale can be rather harmful in the extreme but remember, Confucius, said: “do everything in moderation even moderation.” We aren’t seeking numerical perfection as that is unrealistic; we are seeking balance. Your pH is always going to lean to one side or the other of perfectly neutral. When we maintain a pH of 7.4 - 7.6, we provide some elbow room between our pool's normal operating condition and a corrosive, potentially hazardous environment. This is particularly important when we take into consideration the fact that the pH scale is logarithmic, meaning that every increase in a unit of measure is ten times that of its predecessor. If our pH swings slightly high, that alkaline condition will not likely cause any real lasting damage before it is identified and rectified. Our window of time to address pH that swings below 7 however is much smaller before pretty bad things begin to happen to our pool finish and metallic equipment components.

There are several chemicals that can be used to adjust pH either up or down. Some are used for specific purposes like the rapid increase or decrease of a pH condition, preparation for certain types of pool maintenance, or because they are regionally available. The most common chemicals used to maintain proper pH however are by far Muriatic Acid and Sodium Carbonate, known colloquially as Soda Ash. These chemicals are available at virtually all pool retail establishments and are sufficient for maintaining proper ph.

Total Alkalinity (TA) - ideal range: 80 to 120 ppm

Total alkalinity is, in my opinion, a bit of a misnomer or at least somewhat misleading in the name. When we’ve referred to alkalinity up to this point, it has been in relation to the pH reading on the 0-14 scale (remember anything above 7 is basic or alkaline). With total alkalinity we are referring to a measure of the ionic compounds present in the water that resist change in the pH of the water; in this case sodium carbonate, sodium bicarbonate, and sodium hydroxide. Bored? Confused? Not to worry. It isn’t necessary to know those compounds intimately. The important thing to remember is that TA is a measure of your pool water's ability to buffer rapid pH swings or bounces. This buffering ability is important because it allows your pool service professional to maintaining stable long-term pool water conditions that are both safe and sanitary.

There are a few common syndromes that occur when TA is either too high or too low. Low total alkalinity typically occurs when there is a deficit of bicarbonate ions in your pool water. This reduction in your buffer allows relatively small amounts of chemical inputs to have dramatic impacts on your ph. This condition is known as pH bounce. When your pH is not reliably stable not only is your water quality poor, you can be led down a path of trying to hit a moving target with various chemical cocktails in a reactionary attempt to stabilize your imbalance. Aside from being costly and wasteful, this approach is ineffective because the foundational stone that holds your pool chemistry stable, your pH, is not dialed in; and so the whole row of dominos comes down. Low alkalinity is a caustic water condition and can result in the etching of the metallic components and finished surfaces in your pool. You may even see evidence of copper in your water manifest in a green tint, which is quite likely being stripped from the copper heat exchanger on your equipment pad.

As this pendulum we are on the swings to the opposite extreme, high total alkalinity is the result of a glut of calcium carbonate present in your pool or spa water. In high TA conditions, you may experience pH lock, in which your pH is extremely difficult to correct. Many associated symptoms of high TA are exactly what you may expect from the mineral-rich water in the Mojave Desert taken to the extreme. Excess calcium carbonate suspended in your pool water will make the water cloudy and filmy. It will also calcify your water line tile, coping, stonework, and pool equipment. That material will occlude your pool filters which will reduce the volume of water flowing through your circulation system which in turn will affect nearly every piece of equipment downstream from the intake manifold including your pump, filter, UV system, salt chlorine generator, heater, in-floor cleaner, spa jets, and water features. In many cases, high TA and the resulting reduction in volumetric flow through your heater will result in the demineralization of your pool water inside the very hot copper heat exchanger. When this occurs that excess material will adhere to the inner walls of the heat exchanger tubes, causing a reduction in the tube diameter and available water flow, overheating, and rapid failure of the heater. This is the type of damage that can cost thousands of dollars to repair and just to be clear, chemical damage is not covered by your manufacturer's warranty. High total alkalinity can be a serious issue and is a very common problem in southern Nevada. You can reduce your TA through the use of liquid muriatic acid or sodium bisulfate in granulated form. If severe enough, a high total alkalinity condition in conjunction with high calcium hardness may require the pool to be drained completely, acid washed, and bead blasted, then refilled to start the chemical balance from scratch.

Calcium Hardness (CH) - ideal range 150 to 400 ppm

Calcium hardness is interesting, and I think misunderstood in a similar way to total alkalinity. At first glance, you might be inclined to think of CH only in the context of hard water and the resulting scale or calcification. It is true that high calcium hardness tends to clog filters, calcify surfaces, and cloud water in the same way described in high total alkalinity but remember our theme of balance here. Visualize the pendulum swinging back and forth from one extreme to the other as we try to coax it toward neutrality through chemistry. Going back to our second paragraph, water will balance itself using whatever is most readily available in the environment. If your pool is experiencing a low calcium condition, that water is going to seek to satisfy the imbalance by incorporating the calcium in your plaster, pebble, grout, and stone into the solution until equilibrium is restored. It’s sort of miraculous and wonderful how it works, and unfortunately highly destructive to your pool.

In the American Southwest where I sit writing this, we will rarely if ever experience low calcium content in our water. Calcium carbonate is a naturally occurring salt found in limestone, chalk, calcite, and aragonite. I doubtfully need to point out that we have those minerals in abundance encasing the aquifers that hold the water we use to fill our pools. We’ve covered many of the symptoms of high calcium in our water already so I won’t belabor the matter, but there are other problems that may become exacerbated by high CH. Proper water balance is essentially impossible to maintain at CH levels above 1,000 ppm. All that calcification on your pool finish creates a more suitable environment for microbes and algae to develop.

The problem is destructive to your surfaces, and so is the solution. Acid washing and bead blasting degenerate the finish material of your pool, accelerating the aging process of your investment. To complicate things even further, the higher your water temperature is, the less soluble calcium becomes. A problem for the very hot Mojave, and a serious problem when you run that highly calcified water through a 400,000 BTU pool heater. I’ve seen brand-new heat exchangers fail in six months due to scaled tubes. I’ve also seen manufacturers deny just about every warranty claim where scaling due to high calcium hardness and high total alkalinity are the cause of failure because the condition is perfectly preventable with proper care. Even when professionals are involved, it is ultimately our responsibility as pool owners to see that proper water conditions are being met at all times.

Lowering calcium hardness in your pool or spa almost always involves partially or completely draining the body of water and starting over fresh.

Calcium chloride in either hydrated or granulated form is used to raise CH. I strongly recommend hiring a pool professional to apply calcium chloride to your pool as it can be hazardous if improperly handled. Calcium chloride generates significant heat when added to water and poses a potential burn hazard if mixed incorrectly.

To Sum It All Up - sort of

Maintaining your swimming pool or spa water balance properly is no small matter. Anyone can bee-bop through your backyard once a week and “splash and dash” a few cups of liquid chlorine and acid and get passable results until something goes wrong. It is important we educate ourselves about pool water basics so that we may have an extra set of eyes on any potential early warning signs and get out ahead of any problems that may occur as a result of that pendulum swinging too widely one way or the other. An ounce of prevention is worth a pound of the cure, as they say. Keep your finger on the pulse of the basics, and you can save yourself a lot of hassle and money by prolonging the healthy operating condition of your pool, spa, and equipment set.

This is a voluminous topic, and we intend to get into a lot more detail about things like testing procedures, sanitation, alternative sanitation, filtration, circulation, and how it all can relate to a more positive swim experience in subsequent articles. I hope this has helped in some way.


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