All pool water clarity and sanitation questions and condition must start with a quality water test. This test can be done by either your local pool professional or by yourself if you have a test kit that performs several basic tests, including Free Chlorine, pH, Total Alkalinity and Calcium Hardness. An alternative to a multi-test kit is the extremely easy and convenient 5-in-1 test strips. The vast majority of water related problems can be resolved within the parameters of these simple tests. A multi-test kit or 5-in-1 test strip might be the best investment you can make for you and your pool!

Proper chemical treatment is needed in order to prevent a wide range of potential problems including scale and stain formation, colored or cloudy water, corrosion of pool surfaces or equipment and to assure proper performance of the sanitizer being used.

There are five chemical factors that affect water quality. These are listed below in order of importance along with their ideal levels.

pH

Proper Level: 7.2 - 7.8 ppm (parts per million)
pH is the term used to refer to the degree of activity of an acid or base in the water and is the most important factor in swimming pools. pH is measured on a scale from 1 to 12 with 7 being neutral. Pool water pH is best kept in the range of 7.2 to 7.8 ppm.

When pH remains below 7.2, the water is considered to be corrosive. This means etching of plaster and metals in equipment such as heat exchangers will result. In addition, it is more difficult to keep chlorine in the pool because while more effective as a sanitizer at the low pH, chlorine is also much less stable resulting in the consumption of larger quantities of chlorine than would be used at normal pH levels.

Maintaining the pH higher than 7.8 will increase the tendency to form scale or cloudy water. Calcium, the major component in scale, is a relatively unstable mineral and when the pH is high, the calcium is not as soluble and it will have a greater tendency to precipitate or "fall out" of solution resulting in cloudiness or scale. High pH will also reduce chlorine effectiveness resulting in the need to maintain higher chlorine levels to achieve maximum sanitation. If the pH is low, sodium carbonate, otherwise known as pH Up/Increase or soda ash, is added to raise the pH. If the pH is high, pH Down/Decreaser is used. pH Down comes in two forms Liquid acid (muriatic acid) or dry acid (sodium bisulfate).

Alkalinity

Proper Level: 80 - 120 ppm
Total alkalinity refers to the ability of the pool water to resist a change in pH. The key purpose total alkalinity serves is to help manage or control the pH in the pool. It does this by acting as a buffer so that when materials are added to a pool that would otherwise cause the pH to go up or down, these changes are controlled and do not result in severe changes to pool water balance.

When a substance is added to pool water that could effect the pH, total alkalinity will react to neutralize it and help keep the pH in the desired range. Total alkalinity does not determine what the pH will be, but rather acts to help keep the pH in the ranged desired.

When the total alkalinity value is less than 80 ppm, the water can become aggressive and the pH can swing easily upward and downward and back again. If the value is higher than 120 ppm, the water can become cloudy and scale forming and the pH will tend to drift upward.

In adjusting total alkalinity downward, the same acids used to lower pH are employed. When reducing total alkalinity, it is best to add small amounts of acid, either liquid or dry, over a period of several days as opposed to making large adjustments rapidly. Adding too much acid at once may result in lowering the pH so severely that corrosion of pool surfaces and equipment may result. When raising total alkalinity, sodium bicarbonate is the chemical of choice and the required amount can be added all at once.

In cases where the pH is low and the total alkalinity is high, raise the pH first into the normal range of 7.2 to 7.8 and then lower the total alkalinity. When the total alkalinity is low and the pH high, raise the total alkalinity first and then reduce the pH.

In all cases, never add acid to the pool water if the pH is less than 7.2, even if the total alkalinity is high. Instead wait for the pH to rise first before proceeding. If the pH does not come up by itself after a day or two, you will need to add some pH Up before proceeding.

Calcium Hardness

Proper Level: 100 - 400 ppm
The Sum of all the calcium dissolved in water is referred to as the calcium hardness. . The term hardness is now used only to refer to the level of calcium. The term soft water refers to water with lesser or no levels or calcium.

Calcium is important since high levels are unstable and become even more unstable if the pH or the total alkalinity rise above the normal levels. These imbalances can result in cloudy water and/or scale. In addition, calcium does not like warm water. As water temperature rises, calcium becomes more likely to precipitate out of solution. Calcium is actually more soluble in cold water, which is why scaling of heater equipment is so common (picture the inside of a tea-kettle.).

Adding calcium chloride (hardness increaser) to the water easily raises calcium levels. Conversely, there is no simple chemical addition that can be made that will reduce calcium hardness. The only way to reduce calcium hardness levels in pool water is through dilution with water of a lesser hardness.

Over time, calcium hardness will naturally increase in pool water due to evaporation and possibly other factors unless the pool water is regularly diluted.

The best way to minimize the effect of high calcium levels is through the use of a sequestering agent. A sequestering agent is a compound that, when added to water, will chemically bond with calcium and other minerals to make them, in a sense, more soluble. This means that calcium will still be present, but in a form that is less likely to cloud water or form scale if the pH or other factors get out of balance.

Stain Producing Minerals

Proper Level: Absent
The use of sequestering agents becomes even more important in the control of stain producing minerals. Problems of stain formation on pool surfaces or colored water are most often associated with the metals iron, copper and manganese.

Each of these metals can enter a pool by several means and will react in very different ways. One of the most common ways these metals can enter the pool is via the fill water. Therefore, before filling a pool, always be certain to have the water tested for all three metals in additional to the other chemicals parameters. In this way you will be better prepared to deal with the initial pool treatment.

Iron
When dissolved in water, iron is colorless but will react almost instantly with chlorine and other oxidizers to produce a rusty red color in water, or worse, orange colored staining. As little as 0.1 PPM of iron is all that is needed to result in colored water and stains. The most common source of iron in pool water is the fill water. Often times when large quantities of water are drawn from municipal pipes, such as when a pool is first being filled, the heavy flow of water can cause iron bearing sediments laying in the pipes to be stirred up, causing them to enter your pool unexpectedly.

Copper
Copper is a common cause of green water and stains ranging in color from blue-green to black. Copper algaecides are also frequently implicated in causing stains in pools. In some cases, the copper algaecide may be responsible because the chemical complexing agents in the product used to keep the copper in solution may be of lesser quality and thus allowed the copper to prematurely precipitate. However, a more common cause is likely how the product was applied to the pool in the first place. Copper algaecides come in several types and some are more prone to staining than others. However, copper algaecides are usually very concentrated, requiring only a very few ounces to be applied for each 10,000 gallons of pool water volume. Often times, label directions are not followed and a significant overdose occurs. In these cases, the chance of stains increases dramatically.

Manganese
Manganese is the final metal that can lead to problems, and will color the water from pink to deep purple depending on the level present. Manganese only enters the pool from the source water either through natural occurrence or after being intentionally added by a water treatment plant in the form of potassium permanganate. The latter causes problems when it is inadvertently overdosed and then arrives at the pool when filling or adding water. Again, the biggest problem is that you simply do not know when the water may contain manganese.

The important thing to understand is that all three metals can easily be kept from causing problems with the regular use of a sequestering agent. As with preventing problems with calcium, the sequestering agent will chemically combine with the metals in the water and keep them from precipitating out of the water to cause staining.

The best time to use a sequestering agent is when the pool is being filled for the first time, and thereafter as part of a regular preventive maintenance program. In this way, any metals that may be present in the fill water will be tied up or inactivated before they can cause a problem. Also, by adding the sequestering agent as part of the regular maintenance program, the pool will be protected from stains even when you did not expect metals to be present. It is far easier to prevent staining caused by metals than to remove the stains once they have formed.

Total Dissolved Solids

Proper Level: 250 - 1500 ppm
Total dissolved solids (TDS) are normally the least worrisome factor. TDS is the sum of all materials dissolved in the water and normally runs in the range of 250 ppm or higher.

There is much discussion over what levels are considered too high, but there is no real lower limit. TDS is comprised of many different chemical compounds, which means that the issue of how much is too much actually depends more on what they consist of than how much there is. For example, sodium chloride or ordinary salt is extremely soluble and is therefore unlikely to cause a problem, whereas, as we have seen, calcium compounds can be a problem even at fairly low levels. in general, when the TDS exceeds approximately 1,500 PPM, problems may begin to occur.

It must be pointed out that pools whose sanitizing systems are based on chlorine or bromine generation equipment will likely have much higher TDS levels. These pools actually have salt in one form or another added to the pool. The salt used is highly soluble and does not cause the type of problems normally associated with high TDS, but never the less, it does add to the TDS level in the pool. When testing water in this type of pool for TDS, the salt intentionally added to the pool needs to be taken into account.

At elevated levels, TDS can lead to cloudy or hazy water, difficulty in maintaining water balance, reduction in sanitizer activity and foaming. Unfortunately, the only way to reduce TDS is to drain a portion of the water and replace it with fresh water. Sequestering agents do not help when high TDS levels are causing cloudy water.