Sanitizing and Balancing Your Pool Water

Disinfecting is an essential element of any pool water treatment program and is the whole reason why we put chlorine in the pool in the first place. Stabilized Chlorine is designed to disinfect your pool water by releasing "free chlorine" into the water to control germs and other microorganisms, algae and organic matter. Because water conditions change rapidly, it is very important to test the water every 4 hours for chlorine residual. The free available chlorine reading should be between 1-2 PPM the chlorine to have the required effect the pool water needs to be balanced. Its not that hard but it is very useful to understand what to do and why you do it.

Pool Water Balancing

Continuous filtration and disinfection removes contaminants which keep the water enjoyable but this is does not balance your water. Everything that comes in contact with your pool water will affect its balance; oils, dirt and cosmetics, anything.

Balanced water may be said to be neither corrosive nor scaling, over nor under-saturated.

Scaling or Over Saturation

Scaling is like when you dissolve, spoonful after spoonful of something in a glass of water until it will dissolve no more into solution, and the grains just sit on the bottom of the container.

In the case of a pool its minerals that wont dissolve. Water which is over-saturated will attempt to throw off some of its content by precipitating minerals out of solution in the form of scale.

Corrosive or Under Saturation

Corrosive or aggressive condition is when water is considerably less than saturated. The cliché that "water seeks its own level" certainly applies here. Water which is under-saturated will attempt to saturate itself by dissolving everything in contact with it in order to build up its content.

Water in a Commercial Pool

Water in a commercial pool is tested every 4 hours to discover if it is over or under saturated? The level of saturation is measured by checking that the water has proper levels of pH, Total Alkalinity, and Calcium Hardness.

pH and Water Balance

pH is one of the most important and misunderstood factors in pool water balance and it should be tested and corrected.

The pH of our eyes is about 7.2, so it’s only logical therefore that the ideal pH for your pool is just that - 7.2. This is also the pH of tap water in most developed world countries.

pH is a measure of the basicity of an aqueous or water based solution. That is, pH measures if the water is more acidic or more basic. Pure water is said to be neutral, with a pH close to 7.0 at 25 °C (77 °F). Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are more basic.

pH and Basicity

Basicity is a chemistry term which actually measures the transfer of ions but in the context of a swimming pool, refers the level of acidity of a pool compared to its alkalinity (thus using alkalinity as its base. Hence the higher the pH is more basic). However for the purpose of simplicity basicity and alkalinity are often used interchangeable as they are here. In other words, pH in pool water is the measure of the relative acid or alkalinity in the water.

Acceptable pH Levels

The acceptable level for swimming pool water is between 7.2 and 7.8.

Maintaining a Correct pH Level

To maintain a correct pH level in your swimming pool water, you need to use a pH Increaser when the pH drops below 7.2 and a pH Reducer when the pH rises above 7.8.

A pH below 7.2, it is "too low" and the following is will occur:

  • If the swimming pool is Marbelite or plaster, the pool water will begin to dissolve the surface, creating a roughness which is ideal for pool algae growth. A similar result occurs in the grouting of tiled swimming pools.
  • Metals corrode - and this includes swimming pool equipment, pipe fittings, pump connections, etc.
  • As the swimming pool walls and metal parts corrode, sulphates are formed. These sulphates are released from the water onto the walls and floor of the swimming pool causing ugly brown and black stains.
  • Chlorine, which is used as a disinfectant in the swimming pool water, is activated and lost to the atmosphere very quickly. The water is not being sanitized, and we are throwing away our money by adding chlorine when the pH is too low.
  • When we swim, our eyes and nose burn. Our swimwear fades and perishes. Our skin gets dry and itchy.

A pH level above 7.8, it is "too high" and the following is will occur:

    What happens when the pool is too alkaline (pH is high)?
  • The calcium in the swimming pool water combines with carbonates and forms scale, just like in our kettles. This calcification is seen most at the waterline, where it traps dust and dirt, turning black with time.
  • The swimming pool water starts to become cloudy or murky and it loses its sparkle.
  • The calcium carbonate has a tendency to plate out on the sand in the swimming pool filter, effectively turning it into cement. So your sand filter becomes a cement filter, and loses its ability to trap dirt from the pool water.
  • As the pH rises, the power of the chlorine to act on foreign particles is lost. At a pH of 8.0 the pool can only use 20% of the chlorine you put in. So 80% of it goes to waste and you would need 5 times as much chlorine to provide the disinfection you need.
  • In alkaline swimming pool water, the swimmers suffer too. Our eyes, nose and skin gets dry and itchy.

Swimming pools therefore save money on chlorine by making sure the pool's pH is in the appropriate range.

By neglecting to test and correct the pH of swimming pool water, we not only cause it to become unsightly, but we also cause ourselves physical discomfort. In addition to this, we insist on throwing away our hard-earned money on swimming pool chemicals that cannot possibly be effective in that pool water.

Total Alkalinity

Total Alkalinity is not the same as having a more basic or high pH but it is a close cousin of pH. Whereas pH effectively measures level of acidity compared to alkalinity, a measurement of the total alkalinity in the water is a measurement of all carbonates, bicarbonates, hydroxides, and other alkaline substances found in the pool water. pH is alkaline dependent so that good Total Alkalinity makes it much easier to maintain good pH. In fact alkalinity is defined as the ability of the water to resist changes in pH.

For "gunite" and concrete pools: the appropriate range for Total Alkalinity is between 75 and 120 ppm (parts per million). High Total Alkalinity (above 120 PPM) will allow your pH to slowly creep up and resist efforts to change. Low Total Alkalinity (below 75 PPM) allows your pH to "bounce" from one extreme to the other, making it very difficult to keep your pH in the appropriate range.

Ideal Total Alkalinity can be achieved by adding Alkalinity Increaser if the Total Alkalinity is below 75 PPM and pH Reducer if Total Alkalinity is above 120 PPM.

For painted, vinyl, and fiberglass pools: 125-170ppm is ideal.

Adding an acid or Total Alkalinity Reducer, underwater, in a deep end corner known as “pooling” will create a greater hydrocarbon exchange and have a greater effect on lowering TA in your pool. Acids will lower both pH and alkalinity, but walking the acid around the pool in a highly distributed manner is said to have a greater effect lowering the pH than the alkalinity. Pooling the acid has the opposite effect.

In commercial pools Total Alkalinity is usually only tested for once a day.

Calcium Hardness

When we speak of scale, we are talking about calcium carbonate which has come out of solution and deposited itself on surfaces. It is a combination of carbonate ions, a part of total alkalinity and calcium, and is measured in the Calcium Hardness levels. The test for Calcium Hardness is a measure of how "hard" or "soft" the water is or the amount of dissolved calcium in your pool water.

Hard Water

"Hard" water can have high levels of calcium and magnesium. If these levels are too high, the water becomes saturated and will throw off excess particles (calcium) that precipitate out of solution and seeks to be deposited on almost any surface inside the pool, causing cloudy conditions and scale deposits. They can be attracted to ladders, lights and in extreme cases deposit themselves as very small crystalline clumps - all over the pool surfaces. Calcium Carbonate scale; a "white-ish," crystallized rough nodule.

Soft Water

If the Calcium Hardness levels are too low, the water is under-saturated. If under-saturated, the water will become aggressive as it attempts to obtain the calcium it needs. Such "soft-water" will actually corrode surfaces inside the pool which contain calcium (like pool plaster) and other minerals to maintain its hardness demand.

In most cases you need not worry if your calcium levels are below 500, but much higher than that are the problem. Reducing the calcium levels and preventing cloudy water can be accomplished by dilution (adding water to the pool which has a lower calcium hardness content) or add a Rust and Scale Remover when the Calcium Hardness Level rises above 400 PPM. Levels which are too low require the addition of calcium chloride or Water Hardness Increaser. Recommended range for calcium hardness is 200-400ppm. Calcium Hardness levels should be tested weekly.

Dealing With Stain Producing Metals in your Pool Water

Iron, copper, manganese, and cobalt are metals which commonly cause colored water or stains in pools. If you are fortunate enough to have the "ideal" fill water, and a properly constructed and maintained pool, these would not be a problem. Since ideal conditions rarely exist, we recommend the regular use of a good sequestering agent to continually protect the pool against stain producing metals.

Protecting Your Chlorine from Sunlight

At the start of each season it may be necessary to add Stabilizer. Sunlight can rapidly destroy chlorine residual in outdoor pools unless the pool water is "stabilized". Stabilizer, sometimes referred to as "conditioner", will shield your chlorine from rapid destruction by sunlight. In effect it will make the chlorine you buy last longer, saving you money in the long run.

Recommended Ranges

Recommended Ranges of Swimming Pool Water Chemistry for most commercial swimming pools:

  • pH -7.2 - 7.8
  • Total Alkalinity - 75 - 120 PPM
  • Calcium Hardness - 100 - 500 PPM
  • Free Available Chlorine - 1 - 2 PPM

Making sure that your pool is properly balanced will not only save you money by will look after your swimmers.