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Water Balance Fundamentals
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Water Balance Fundamentals

Pool water chemistry is a very important part of your swimming pool's health. Most people think that simply adding chlorine tabs to their floater is all they need to do to maintain proper water chemistry. The truth is there is a lot more to it than that. The fundamental principal of water chemistry is balance. In pool care, balance means keeping all the components of water chemistry within proper ranges, not too high, not too low.

The First step in maintaining balanced water is chemical testing. Testing pool water with a test kit is the only way to find out how "healthy" your pool water is. This section of our website is made to help you understand what the chemical readings from your test kit mean, and how to use them to correct any problems you may have.

Here are the basic categories that are covered on this page:




Ideal Range: 2-3 ppm (parts per million)

The job of chlorine in your pool is to keep the water clear and sanitary. It does this by killing and removing organics such as algae, and killing bacteria that may pose a threat to swimmers. Keeping a chlorine residual of 2 to 3 parts per million will ensure that algae blooms will not take hold.

Too Low: Low chlorine levels will allow algae to grow. If there is no chlorine for a significant amount of time (days or weeks) your pool will almost certainly turn green with algae.

Too High: High chlorine levels can be dangerous to swimmers. If the chlorine level is very high, swimmers may feel a burning or itching on their skin. Extreme chlorine levels can also bleach out swimming suits.



Ideal Range: 7.4 - 7.6

The pH of pool water may be the single most important part of maintaining balanced water chemistry. In order for chlorine to do its job of killing contaminants the pH must be in the proper range.

Unlike testing for chlorine, when you test pH you are not measuring the amount of something that is in the water; you are measuring the acidity of the water itself. pH is adjusted up or down to try to keep it around 7.5. To lower pH you simply add acid; to raise it you add soda ash (sodium carbonate).

Too Low: When a pool's pH is too low it means that the water is too acidic, needless to say this is a bad thing. There are a number of problems that arise with low pH.

The first effect of low pH is that chlorine becomes extremely active, and is more likely to cause discomfort for swimmers. The long term effects of low pH are more severe. Acidic water will chew up almost everything it comes in contact with, which includes pool plaster, pool heaters, pumps, rubber gaskets, etc. Many a pool heater has been destroyed by water that has improper pH.

Too High: Water with a high pH is called Basic. Basic water will make chlorine unable to do its job of killing bacteria and sanitizing your pool. Cloudy water, plugged filters, and reduced water circulation are all symptoms of high pH.



Ideal Range: 90 - 120

Alkalinity is very closely tied to pH. Essentially alkalinity is a measure of how well your water will hold its pH level. When alkalinity is outside its recommended range pH will swing dramatically up and down, this is called pH bounce. When alkalinity is around 100 where it should be, pH will stay much more constant. Whenever you get a pH reading that is not where it should be (very high or very low) you should check your alkalinity to see if it is what is causing the problem. If alkalinity is off, you always want to adjust it first before you adjust your pH. Once your alkalinity is balanced you can adjust your pH to the proper level and it will be much more likely to stay there.

Alkalinity is adjusted downwards in pools by using muriatic acid (swimming pool acid). In spas, dry acid is used to lower alkalinity. Sodium Bicarbonate is used to raise Alkalinity in both pools and spas. The amount of acid or sodium bicarbonate needed depends on the size of the pool, and the alkalinity level. Please refer to the product you are using for dosage quantities.

Too Low: Low alkalinity will cause the same problems as low pH. Heaters will corrode, plaster will become pitted and stained, and pH will bounce up and down.

Too High: High alkalinity will cause the pH of the water to drift upward. Just like high pH, high alkalinity will cause cloudy water and plugged filters.


Calcium Hardness

Ideal Range: 150 - 400 ppm.

Calcium hardness is a measure of the amount of calcium that is dissolved in your pool water. This is not something that needs to be checked all the time as calcium levels change slowly. Generally calcium hardness should be checked about twice a year. Calcium builds up over time in pool water because there is calcium in the water that is used to fill the pool.

Let's say for example that your tap water has 100 parts per million calcium: When the pool is first filled the calcium level will be 100 ppm. Over time water evaporates out of the pool and is replaced with more tap water. The calcium does not evaporate with the water, and the refill water has calcium in it, so the calcium level increases. Essentially calcium is being regularly added but never removed. Filter backwashing is the only time that calcium is taken out of your pool. When calcium hardness gets too high (over 600 or so) the only solution is to drain the pool and start the cycle over.

Too Low: Water that does not have enough calcium (known as soft water) will actually leech calcium out of a pool's plaster. Needless to say this is not good for your plaster, but low calcium is a very rare condition for a swimming pool. Just be sure you don't have a water softener attached to the fill line.

Too High: Water with too much calcium will try to deposit the excess calcium anywhere it can. Pool tiles will get white crusty calcium scale around the water line. Pool filters will get plugged with hard calcium deposits that are very difficult to remove, resulting in poor circulation. Cloudy water can also be caused by high calcium hardness.


Cyanuric Acid

Ideal Range: 40 - 50 ppm

Cyanuric Acid is the official name of what many pool guys call conditioner, stabilizer, or CYA. The job of CYA is to help chlorine stay in your pool water so that it may do its sanitizing job. Unstabilized chlorine will "burn off" in direct sunlight very quickly leaving your pool water undefended against algae and bacteria. CYA binds to the chlorine to keep it from burning off. The tricky part here is that too much CYA will actually bind up the chlorine so that it cannot do its job at all.

There is some dispute within the pool industry about whether conditioner is really necessary, and how much should be used. Some say it should be no higher than 30 ppm, others say never under 50. In my experience if you keep your CYA level around 50 you won't have any problems. I should note that chlorine tablets come with CYA already in them, so as you add tabs to your pool you are adding CYA. Over time this can cause your conditioner level to increase to the point that a pool drain is necessary to remove the CYA. Regularly backwashing your filter will help to keep the CYA level in check. It is good practice to the check conditioner level about twice a year. If it is over 100, the pool will need to be drained. If it is below 30, it may be necessary to add conditioner.

Too Low: Your chlorine will be unstabilized and will disappear very quickly in the sun. This means you will be adding much more chlorine than you need to sanitize your pool, which can be expensive. A very sunny day could use up all the chlorine in the water and leave the door wide open for an algae bloom.

Too High: The chlorine in the water will become over stabilized and unable to fight off contaminants. Cloudy water and algae are sure to be present when the CYA level gets over 100 ppm, even if you have sufficient levels of chlorine. This will often cause people to add additional chlorine tabs to the water which adds more CYA, creating a self defeating cycle.