It goes without saying that most people associate chlorine with pool chemistry.  The fact is, however, that pool chemical balance goes far beyond just adding chlorine to your pool.  In fact, neglecting the other aspects of pool care can cause corrosion, stains, and calcium deposits.  It’s advised to check your pool chemistry at least once per week as it can change almost day to do.  But before you head to the pool supply store and are sold hundreds of dollars of unnecessary chemicals,  here are the definition and importance of all the chemicals you should become familiar with:

Chlorine

Chlorine is the “bread and butter” to proper pool chemistry.  Its job is to sanitize the water and keep it clear of bacteria.  However there are two variations of chlorine you should know.

Total chlorine (TC)  is, well, the product of sanitation meaning, in laymen’s terms, it’s been used up but is still present in the pool.  If your TC is above 0.5 ppm, it’s advised you “shock” or superchlorinate the pool.

Free chlorine, on the other hand, is the level of chlorine that is available to sanitize.  This level should be kept at around 3.0 ppm to provide a safe swimming environment.

PH/Acidity

All water, including your drinking water, has a desired pH which is the balance of acidity and alkalinity.  Acidic water (less than 7.0) over time can corrode metal components.  Alkaline water (over 8.0) can lead to scale and calcium deposits along pool walls and tile.

Most swimming pools naturally have higher pH over time but this can be greatly effected  simply by the type of chlorine that’s being used.  Liquid chlorine has very high pH so it’s expected to be accompanied by using acid to neutralize.  Conversely, dry chlorine tablets or granular chlorine has very low pH, so there isn’t as much demand for acid here.  PH, more than chlorine, can fluctuate in much greater extremes so it’s advised to check pH every few days.

Calcium

The level of calcium determines hardness of the water.  Pools with soft water, lacking calcium, will draw dissolve from plaster, stone, or concrete.  On the other hand, pool water with too much calcium will leave deposits on plaster and tile.  The only tangible solution in this case is to drain a few inches of water from your pool and replace with fresh water.

Cyanuric Acid (CYA)

The last component to a chemically-balanced pool is cyanuric acid (CYA), sometimes promoted as “stabilizer” or “conditioner”.  The purpose of cya is to provide, essentially, a protective barrier for chlorine.  Chlorine is highly unstable, which means as quickly as you dump a jug of it into the pool, it can very easily be destroyed, mainly from UV rays from the sun.  CYA, therefore, provides a shield between the sun’s rays and chlorine.  Without cya, a full jug of chlorine can be rendered useless in a matter of days, especially in long and hot summer days.

“So more cya must mean longer lifespan of chlorine, right?”

Up until a point, the answer would be “yes” however, be careful not to let your cya levels get to high as your chlorine can become “locked” or useless.  If you find yourself in this predicament, simply drain your pool about 6 inches and add back in fresh water or until cya levels come back to about 100.

One noteworthy item regarding cya is that dry chlorine, both in granular and tablet form, come infused with cya meaning over time, your cya levels will naturally rise with continued use.

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There are many more chemicals and sanitizing agents that can be discussed here, but if you’re just starting to handle your own pool service, this is a great starting guide.