Barack has expertise in pool chemistry and pool maintenance. He writes in-depth articles about how to maintain pools for optimal enjoyment.
First Things First: How Chemically Safe is your Swimming Pool?
There are only two main reasons why we use chemicals in our swimming pools: For health reasons, and to have a clear pool water.
This article includes in the bottom section, all pool chemicals that you cannot do without, such as pH chemicals, Chlorine, Calcium, Alkalinity Increaser, Cyanuric acid, Algaecide, Pool water Clarifiers, Pool Flocculant, and others; including how and when to use them in your pool.
But first, as a chemical engineer, I thought you should know; there is nothing more dangerous like pool chemicals we use in order to maintain the status of our pool water.
According to a study by Municipal Institute of Medical Research published on American Journal Epidemiology, swimming pool chemicals (especially chlorine) are harmful when inhaled, ingested, or absorbed through the skin.
According to the same study, disinfection by-product of chlorine called Trihalomethane (THM) is linked to an increased risk of bladder cancer by 57% percent.
To add on top, when these by-products are absorbed through the skin or inhaled through the lung since they can't undergo detoxification in the liver, they may cause more powerful carcinogenic effects.
In short, most of the studies I have come across stress that pool chemicals and their by-products are dangerous; by-products even more dangerous than the chemicals themselves.
Never the less; we cannot avoid using chemicals in our swimming pools since they kill or remove harmful bacteria, organisms, and other wastes.
Consequently, the only way to keep our pools safe for swimming is to adopt the most effective and good use of these chemicals. Or maybe, consider switching to a saltwater pool (like I did), which uses a chlorine generator to introduce a chemically less harsh/harmful chlorine in the pool.
Using the Right Chemical for the Right Pool
Now for more than 5 years, I have been working on several pools with different water quality: Some with lots of metal components, others with nitrate content, and some with lots of organic waste deposits, others with accumulated stabilizer, and others with a high rate of suspended matter.
Succinctly, I have learned that all swimming pools cannot be treated the same way and with the same chemicals. Most pool managers have trouble maintaining clear water simply because they use chemicals blindly without knowing much about them, and their long-term effects on the water they are treating.
Swimming pool management is all about good filtration system, constant water testing, and use of proper chemicals in the right water, period. You need to be aware of what brand of chemical you are using in your pool.
There are a number of chemicals out there, and most of them come with lots of potential problems: Unfortunately, the chemical manufacturer will not alert you of the potential problems with their chemical.
Use the wrong brand of a chemical in wrong water and you create a whole set of new problems that are costly and time consuming to reverse, like clearing cloudy pool water or getting rid of pool algae.
This article includes everything you need to know about pool chemistry: All types of pool chemicals available, when you need to use them, and which ones to avoid. But first, you may be asking yourself this question:
After How Long Do I Test for Pool Chemicals?
Before I say a lot about pool chemicals, let me remind you that you cannot have clear pool water without an accurate pool water test kit. You will not use any chemical in a pool successfully without knowing accurate readings of all other chemicals in the pool.
Ideally, the question of after how long do you need to test your pool water varies since every chemical has its recommended test period, some are to be tested on a daily basis, others on a weekly basis, and some may go up to a month like Total Alkalinity.
Wrong balance of sensitive chemicals such as pH will affect functions of all chemicals in the pool.
Consequently, you need to have reliable and accurate water testing equipment that will give the exact reading of chemicals in the pool before increasing or reducing their levels.
The bitter truth is; most test strips that you find in the market are never accurate, and are not the best choice when it comes to finding exact values, especially in a commercial pool.
I use LaMotte ColorQ Pro 11 digital pool water test kit to find accurate reading of chemicals, which is very accurate, easy to use, and capable of carrying a number of tests including pH, Free Chlorine, Combined Chlorine, Cyanuric Acid, Calcium Hardness, Bromine, Total Alkalinity, and metals including Copper, Iron, Biguanide, Biguanide Shock.
To know the exact amount of every chemical to add into the pool, I enter the values I get from this digital pool water test machine into Pool Calculator software, and bam, I find accurate values of chemical my pool water needs.
Important Swimming Pool Chemicals
There are chemicals you cannot do without if you need a trouble-free swimming pool. Here are the must have pool chemicals:
1. The pH Adjusters
The pH test is one of the most important water tests, which you need to carry at least once a day until you get enough experience with your pool.
Truly, different individuals and organizations have recommended different values for pH all over the internet and this is somewhat confusing.
However, the safest and widely recommended reading for pH in a pool should be between 7.4 and 7.8, however, with 7.6 as an ideal level for swimming in most regions.
If the pH is allowed to reach high ends of 7.8 or above, none of the chemicals you add to the pool will work for you, including important free chlorine. Moreover, this may also cause calcium scaling in the pool water.
Also important, some newly made plaster pools will drift up towards higher pH because of soda ash present in the materials used, but this problem should reduce over time and should not cause an alarm.
On the other hand, pH levels below 7.2 tend to burn eyes: Much lower pH levels of 6.8 and below may also cause damage to metal parts, especially on pool heaters made with copper parts in them.
If your pool water is full of copper components higher than 0.02 ppm for any reason; maintaining pH at the levels of 7.3 to 7.4 is recommended to take care of the copper contents in the pool water.
You can use pH raisers such as soda ash and baking soda (sodium bicarbonate) if the reading goes below the recommended value. A good example of sodium carbonate is known as PH Increaser.
On the other hand, you can use sodium bisulfate, which is also known as pH Reducer, or muriatic acid to lower pH level if it goes beyond the normal required range.
Some pH control chemicals have potential problems and may affect the functionality of other important chemicals, especial total alkalinity; and you need to be careful when selecting pH control chemicals.
Chlorine is one of the most important pool chemicals you need for your pool. Chlorine test is very important and needs to be done at least once or twice a day. There are two types of chlorine: Free chlorine and Combined chlorine. Total chlorine is Free plus Combined chlorine.
Free Chlorine (FC)
If you need to keep a good balance of your pool water and chlorine, free chlorine is the most important chemical to be tested daily and maintained within the required range.
However, if you are using saltwater chlorine generator (SWG), you may test for free chlorine after every two days since chlorine is automatically tested and added by chlorine generator.
Free chlorine is consumed a lot by direct sunlight and when killing organic matters in the pool. Allowing free chlorine to go much lower will lead to pool algae thriving in the pool, and you don't want to go through the frustrating process of removing pool algae.
Free chlorine levels should be kept around 2.5 ppm or above. Apart from killing organisms and other bacteria in pool water, keeping free chlorine within the required range also assists in precipitating out iron components in the pool.
Precipitated iron can easily be removed by DE pool filter: As such, DE filter is recommended for pools with lots of iron components since it filters down to 4 to 9 microns.
Finally, if your pool has Cyanuric acid, the level of free chlorine will vary depending on the available Cyanuric acid in the pool water.
Have a look at Chlorine/Cyanuric chart to know appropriate free chlorine to add to the pool with Cyanuric acid content.
Combined Chlorine (CC)
Combined chlorine, also called chloramines, is formed as FC is consumed. It produces a smell associated with chlorine in chlorinated pools.
The levels of CC should not go beyond 0.5 ppm, and if does, it is time to shock your pool. Always ensure that CC is maintained at zero since higher CC shows that FC is very low and it needs to be raised.
If you use potassium mono persulfate, which is a nonchlorine shock, you need to neutralize it in order to get the true value of CC: This is necessary since potassium mono persulfate will show as CC when a test is done.
Here are different types of chlorine shocks that you can use to chlorinate your pool depending on different circumstances.
Calcium is another important pool chemical used mainly to protect pool parts. Calcium hardness test is done to indicate the total amount of calcium in the pool water. This can be done at least after every one month.
For plaster pools, you need to keep calcium hardness between 250 and 350 ppm. Pool water with low calcium levels will dissolve calcium out of plaster, tiles, concrete, and fiberglass used in the pool.
Moreover, keeping calcium hardness in the range of 350 ppm also reduces negative effects of copper in the pool water.
It is also advisable to keep calcium at 100 to 150 in spa pools to prevent foams. To increase calcium levels, you can use calcium chloride like Pool Calcium Hardness Increaser. Unfortunately, to lower calcium levels; the recommended solution is to replace the pool water.
4. Total Alkalinity (TA)
Total alkalinity should be tested after every one month. TA is the resistance of water to changes in pH levels.
TA should be kept between 80 and 120 ppm for pools with liners and between 100 and 125 ppm for pools made of plaster.
High levels of TA will make your pH level go up. High total alkalinity also causes calcium scaling and should be lowered immediately if it goes out of range. Here is the most appropriate way to lower total alkalinity when it goes above the normal range.
To lower the Total Alkalinity, the best way is to add acid to lower your pH between 7.0 and 7.2; which will also lowers the TA: Then aerate until pH rises to about 7.6; this will raise pH without raising the TA levels.
If the TA is not yet at the required levels, repeat the same process till you get the right balance of TA.
You only need to lower the TA when pH levels are rising rapidly, or when TA is causing calcium scaling through calcium saturation index (CSI).
You can raise TA levels slowly by the use of baking soda or Alkalinity Increaser: Adding large amounts of baking soda may raise your pH more than recommended levels.
5. Cyanuric Acid (CYA)
Cyanuric acid is used as a stabilizer in outdoor pools. It should be tested at least after every one month.
CYA protects free chlorine from direct sunlight, which consumes FC at very high rates.
The amount of Cyanuric acid in a pool will depend on the amount of free chlorine available: The higher the CYA levels in a pool, the higher the FC the pool will need.
The recommended range of Cyanuric acid should be 30 to 50 ppm for nonsalt water pools and between 70 and 80 ppm for saltwater pool system. If it is necessary to use in indoor pools, keep CYA between 0 and 20 ppm.
You can increase CYA levels by adding Cyanuric acid sold locally as stabilizer or conditioner. The liquid Cyanuric acid is more effective than solid stabilizer since it dissolves in water much faster.
Unfortunately, there is no chemical that can be used to reduce Cyanuric acid when it gets out of range in a pool: To reduce CYA levels, the recommended solution is to drain and replace your pool water.
6. Pool Water Clarifier and Pool Floc (Flocculant)
Sometimes, a cloudy pool water becomes too difficult to clear up, especially when you don't know the course of cloudiness.
If chemicals are all balanced in your pool and the filter is working properly without any default but your pool water still appears cloudy, chances are high that you have dirt or debris in your pool that makes the water to be cloudy.
Pool water clarifier is used to collect all the fine debris present in the pool water so that the pool filter can remove them clearing the cloudy pool.
When the debris in your pool are a little larger, you are supposed to use Pool Floc (Flocculant), which collects all the cloudy particles to the bottom of your pool making a large cloud of particles at the bottom of the pool. The pool is then vacuumed manually using a pump to remove the particles and clear up a cloudy pool.
Algaecide is one of the most important swimming pool chemicals you must have. Algaecide is used in the pool to prevent algae breakout or to get rid of algae in the pool that turn pool water green, yellow, or black depending on the type of pool algae.
Though, if your pool is sanitized using chlorine shock on a frequent basis, algaecide may not be necessary to use unless there are signs of algae starting to show up on the pool walls, water, or other pool parts.
However, some people use algaecide in their pool once a week to help prevent algae, especially in a hot and humid climate when algae breakout is too common in the swimming pools.
Optional Swimming Pool Enhancers
The chemicals discussed above are the major chemicals that you need to maintain clear pool water.
However, some swimming pool managers prefer using extra pool enhancers which I consider not necessary at all until it is very necessary.
Most of the pool enhancing chemicals are used to keep algae in check, and some other uses indicated below.
Since chlorine is necessary for almost all pools, and chlorine kills organisms like algae and more, what is the need to use other enhancers that may cause even bigger pool problems? Only use these products when you have to use them. Anyways:
Borate is one of the optional pool water enhancer used to keep pH levels in balance to avoid drifting and to keep algae growth in check. If at all you prefer using Borate, the recommended level is between 30 to 50 ppm.
I recommend using borate products in metal laden pool water, which requires pH level to be maintained around 7.2 and a reduced use of chlorine to avoid metal staining. See how to fix metal stains in the pool.
Phosphate is another pool chemical used to keep algae in check. I know of some neighbor who was fond of using Phosphate in the pool in the name of avoiding algae.
Eventually, Phosphate levels became too much, resulting in a cloudy pool water. He had to incur the expense of buying phosphate remover to reverse the status of his pool water. I hope the same story does not apply in your case:)
Sequestrants are also very important pool chemicals I thought you should know about. Sequestrants such as Metal Magic are normally used in a metal-laden pool water to avoid metal staining.
Polyquat 60 is another important chemical to know about: This chemical is mostly used to prevent algae when treating metal stains; where chlorine must be lowered to 0.0 ppm for ascorbic acid to work in removing metal stains.
Ascorbic acid or Vitamin C is also a very important pool chemical; which is mainly used to fix metal stains in the pool water or pool equipment.
Taking Care of Total Dissolved Solids (TDS) in the Pool
Total Dissolved Solids is the reading of all materials dissolved in the pool water.
TDS may be dissolved organic or inorganic matters, chlorine residues, calcium, body oil, carbonates, urine, phosphate and much more.
Excess TDS may cause a number of pool problems like health hazards, cloudy, or green pool water and more. The reading of total dissolved solids in the pool should not exceed 1,500 ppm.
TDS is most common in spa pools where bath load and chances of dissolving matters are high. You can use special TDS test kit to measure and correct your pool status.
Don’t use any chemical to correct Total dissolved solids in the pool. TDS can be corrected by either diluting with water to lower TDS or completely draining and replacing the pool water.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.