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Basic Pool Chemistry 101

Auburndale FL Pool Water TestingHave you ever gotten out of a pool with red eyes because the water had too much chlorine? Or been hesitant to get into a pool because the water looked cloudy? Both of these issues are caused by a chemical imbalance in the water. Understanding your pool’s chemistry is essential to maintaining a healthy pool.

Water balance and sanitation are the two basic elements that you have to understand about pool water.

Understanding Water Balance

There are three ingredients of water balance: pH levels, alkalinity, and calcium hardness. When anyone of these is unbalanced, it could cause damage to your pool or make the pool water uncomfortable.

Balanced pH: 7.4 to 7.6

Pool water should have a neutral pH level between 7.4 and 7.6. If the pH is too low, the water is considered acidic. Swimming in water with a low pH can burn your eyes and dry out your skin. It can also eat away at swimwear and swimming goggles. Along with these negative side effects, acidic water can erode plaster, weaken vinyl lining and strip heat exchangers in your pool.

Water with a high pH level isn’t good either. When the pH level is higher than 7.6, it is considered basic. Water that is basic will leave calcium depositions on the filter and tiles. It will make water cloudy. The most important effect of high pH levels is that it prevents chlorine from doing its job. This means that the chlorine will not be able to effectively kill contaminates and pathogens in the water.

Practically everything, from swimming in your pool to rain, can affect the pH level. That’s why it is important to test pool water daily during the swimming season. You should always have pH increaser and pH decreaser on hand. If the pH level is too low, add pH increaser to the water. If the pH level is too high, add pH decreaser.

Balanced Alkalinity: 100 to 150 ppm (parts per million)

Alkaline helps water to maintain the right pH level without changing dramatically. If you keep the alkaline level between 100 to 150 ppm the water’s pH should be more stable. We recommend keeping alkaline increaser on hand. You should stock more alkaline increaser than pH increaser. You do not need to stock alkaline decreaser. If the alkaline level is too high, most likely the pH level will be too high. In that case, pH decreaser will be the solution.

Healthy Calcium Hardness:  200 to 275 ppm (parts per million)

If you’ve ever lived in a home with hard water, you know how important controlling calcium hardness is. Water with too much calcium will leave hard to remove deposits along the walls of the pool and on the filter. Water with too little calcium can do more damage to a pool. It will cause the water in your pool to corrode plaster, pool equipment and any other possible source of calcium in the pool.

Fortunately, calcium levels do not fluctuate as much as pH and alkaline. When you first open your pool at the beginning of the season is the only time you should need to add calcium hardness if your pool has a low level. If the level is too high, you will need to drain some water from your pool and refill it with water that has a lower calcium level.

Understanding Water Sanitation

Maintaining the correct amount of sanitizing chemicals is just as important as water balance. Chlorine and salt are the main chemicals used to sanitize pool water. You could also use Bromine or Biguanide. These sanitizing agents keep pool water safe from bacteria and microorganisms, like algae, that could thrive in water and be hazardous to swim in.

Healthy Chlorine or Salt Level: 3 ppm

There are 2 different ways to add chlorine to pool water: Chlorine tablets and powered or granular chlorine. If you have a salt pool, you will need a salt chlorine generate to convert the salt into chlorine.

Most people choose to use chlorine tables. They come in 1″ and 3″ sized tablets. The tablets can be placed in a chlorinator, skimmer basket or floating chlorine dispense in the pool.

Healthy Bromine Level: 3 to 5 ppm (parts per million)

Bromine is in the same chemical family, halogen, as chlorine. It is usually used in indoor pools and hot tubs because it doesn’t have a strong smell like chlorine. It isn’t as commonly used as chlorine because it isn’t as effective at killing all forms of algae and it is much less effective in sunlight. We do not recommend using it for an outdoor pool that is in direct sunlight.

Healthy Biguanide Level: 30 to 50 ppm

Biguanide sanitizers, like Baquacil and SoftSwim, are just as effective as chlorine. An additional benefit to using one is that they make water feel smoother.

The downside of using a Biguanide sanitizer is it can’t be mixed with other standard pool chemicals. You have to use shock treatments, algaecides and other pool chemical that are specifically made for a Biguanide pool. The cost of these chemical packages is much more expensive than chlorine-compatible chemicals. Most pool owners choose not to use a Biguanide sanitizer because of these extra costs.

Extra Sanitation Treatments

Pool Cleaning & Maintenance Lakeland FLPool Shock

When chlorine attacks and kills algae or bacteria it becomes what is called “combined chlorine” (CC). Chlorine that hasn’t yet done its job is called “free chlorine” (FC).

Chlorine and salt pools typically need to be shocked at least once a week so that combined chlorine can oxidize and break apart. This is what a shock treatment does. It keeps your chlorine working effectively.

Shock treatments are unstable which means they need to be done at night, after the sun is down, so that the sun’s UV rays cannot affect the treatment.

Water Stabilizer (Cyanuric Acid)

Though chlorine is more stable than bromine, it can still become less effect when it is hit with the sun’s UV rays. Adding water stabilizer or cyanuric acid to pool water will stabilize the chlorine so that it is less affected by the sun.


The purpose of an algaecide is to kill algae. If you maintain healthy levels of chlorine, you should not have to use an algaecide. It can be used as a backup if your chlorine levels have dropped and you cannot get more chlorine soon.

During the swim season, it is important to keep a close eye on the chemical levels in your pool. It will help your pool to last longer and ensure your pool is safe to swim in. Make sure to invest in a good testing kit and test the water once a day or, at the least, once a week.

If you have more questions about pool chemistry or need to pick up supplies for this swim season, stop by PoolWorks! We are always happy to answer questions and carry a wide array of pool supplies to serve residents throughout Lakeland, FL.

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