Sanitizing and Balancing Your Pool Water
Disinfecting is an essential element of any pool water treatment program and that is why we put chlorine in the pool in the first place. Stabilized Chlorine is designed to disinfect your pool water by releasing "free chlorine" to control germs and other microorganisms, algae and organic matter. Because water conditions change rapidly, you must test the water every 4 hours for chlorine residual. The free available chlorine reading should be between 1-2 PPM chlorine to have the required effect the pool water needs to be balanced. It is not that hard and it is useful to understand what to do and why you do it.
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| Your Pool Water |
Pool Water Balancing
Continuous filtration and disinfection removes contaminants which keep the water enjoyable but this does not balance your water. Everything that comes in contact with your pool water will affect its balance; oils, dirt cosmetics, anything.
Balanced water is not corrosive, scaling over or under-saturated.
Scaling or 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, it's minerals that won't dissolve. Over-saturated water will attempt to throw off some of its content by precipitating minerals from the solution as scale.
Corrosive or Under Saturation
A corrosive or aggressive condition is when water is considerably less than saturated. The cliché that "water seeks its own level" certainly applies here. Under-saturated water will attempt to saturate itself by dissolving everything in contact with it to build up its content.
Water in a Commercial Pool
Water in a commercial pool is tested every 4 hours to discover its saturation level. The amount 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 should be tested and corrected.The pH of our eyes is about 7.2, so it’s only logical 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 whether the water is more acidic or basic. Pure water is 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 that actually measures the transfer of ions. In the context of a swimming pool, it refers to the level of acidity of a pool compared to its alkalinity (thus using alkalinity as its base. Hence the higher pH is more basic). However, for simplicity's sake, basicity and alkalinity are often used interchangeably as they are here. In other words, pH in pool water measures the relative acid or alkalinity.
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, 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 will occur:
- If the swimming pool is Marbelite or plaster, the pool water will slowly dissolve the surface, creating a roughness ideal for pool algae growth. A similar result occurs in the grouting of tiled swimming pools.
- Metals corrode - including 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. Creating ugly brown and black stains.
- Chlorine, used as a disinfectant in the swimming pool water, is activated and quickly lost to the atmosphere. 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 will occur:
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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 becomes cloudy or murky and it loses its sparkle.
- The calcium carbonate tends to plate out on the sand in the swimming pool filter. This effectively turns 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 need 5 times as much chlorine to provide sufficient disinfection.
- In alkaline swimming pool water, the swimmers suffer too. Eyes, nose and skin get dry and itchy.
Swimming pools save money on chlorine by ensuring the pool's pH is within the recommended 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, 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 is a close cousin of pH. Whereas pH effectively measures the 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 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 pH to "bounce" from one extreme to the other, making it difficult to keep your pH in the appropriate range.
Ideal Total Alkalinity can be achieved by adding an Alkalinity Increaser if the Total Alkalinity is below 75 PPM and a pH Reducer if the Total Alkalinity is above 120 PPM.
For painted, vinyl, and fiberglass pools: 125-170ppm is ideal.
Adding 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 pH and alkalinity, but walking the acid around the pool in a highly distributed manner is said to have a greater effect on lowering pH than the alkalinity. Pooling the acid has the opposite effect.
In commercial pools, "Total Alkalinity" is usually only tested once a day.
Calcium Hardness
When we speak of scale, we are talking about calcium carbonate which has come out of solution and deposited 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 Calcium Hardness test measures 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 throwing off excess particles (calcium) that precipitate out of the solution and seek to be deposited on almost any surface inside the pool, causing cloudy conditions and scale deposits. They can be attracted to ladders and lights and in extreme cases deposit themselves as tiny 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 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 calcium levels and preventing cloudy water can be accomplished by diluting (adding water to the pool with a lower calcium hardness content) or adding a Rust and Scale Remover when the Calcium Hardness Level rises above 400 PPM. Levels that are too low require the addition of calcium chloride or "Water Hardness Increaser". The recommended range for calcium hardness is 200-400ppm. Calcium Hardness levels should be tested weekly.
Dealing With Stain Producing Metals in your Pool Water
Metals like Iron, copper, manganese, and cobalt commonly cause coloured 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. Regularly use a good sequestering agent to protect the pool against stain-producing metals.
Protecting Your Chlorine from Sunlight
At the start of each season, it may be necessary to add a Stabilizer. Sunlight can rapidly destroy chlorine residual in outdoor pools unless the pool water is "stabilized". Stabilizer, sometimes called "conditioner", will shield your chlorine from rapid destruction by sunlight. 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
A properly balanced pool will save you money and look after your swimmers.
Enjoy
Richard
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