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The Secret Tango of Pool Chemistry

Wouldn’t it be great if you could just fill your pool with water, and then never have to worry about algae growing, or bacteria building up, or the water just becoming a breeding ground for all kinds of nasty contaminants and organisms? Yes, testing the water and adding pool chemicals regularly might be time-consuming and tedious, but it’s absolutely necessary.

A little preparation means a lot less fixing later when your pool becomes overgrown with algae and the water so unbalanced that the only solution is to drain it and start fresh. While keeping your pool clean and properly sanitized may not strike you as fun, it also doesn’t have to be difficult. All it takes is some basic pool chemistry knowledge, the right equipment and chemicals and a desire to keep your pool clean and swimmable condition.

POOL CHEMICALS - the partners that make up the tango

You could diligently fill your pool with fresh water and skim and brush it every day, and the water can and will still get dirty.

Leaves, twigs, flowers, seeds, pollen, dust and other debris continuously fall into your pool. Insects take their final swims in it and birds fly overhead and bomb it. And every time someone swims, they leave behind body oils, hair, dead skin, shampoo, soap, everything we humans put on our bodies and slough off on a daily basis. Water-loving dogs trample mud into the pool in their eagerness to shed their hair, gob and salivate into the water. Not to mention that the pool seconds as a lavatory for nonchalant bathers (wink, wink). The list goes on.

The only thing keeping those contaminants from turning your pool into a black swamp is your sanitiser, probably the single most important pool chemical you’ll ever use. And in order for the sanitiser to work, other water factors must be balanced: pH, alkalinity and calcium hardness.

Finally, you’ll add pool chemicals to treat algae, to clear your pool and to prevent staining if you use borehole water with high metal levels.

All these factors must dance together in perfect tango harmony in order to create perfectly balanced pool chemistry so that you can swim with peace of mind. So, knowing what to use, and when and how to use it, is vital!

This is the secret tango of pool chemistry and these are the tango partners.


Regardless of the type you use, the sanitiser’s job is to keep the water, well… sanitised and safe. This means free of bacteria, viruses, algae and other nasty things that can grow in untreated pool water. You have a few sanitisers to choose from.


The most popular pool sanitiser due to its efficacy and low cost is chlorine.

Chlorine sanitises your pool by oxidizing contaminants. It enters molecules and destroys them from the inside out. Chlorine is effective at killing viruses, bacteria and algae and will also prophylactically prevent algae from growing to begin with.

Chlorine comes in three forms:

  • Granular: You pour chlorine granules into your pool water where they dissolve and chlorine is distributed around the pool by your pool's circulation and filtration system. This isn't a very effective method though. It is time-consuming and there is a chance the chlorine won't be evenly distributed leaving pockets of not-so-sanitised water around your pool, as well as pockets of super-chlorinated water, which can damage your pool lining.

  • Floater: This is slow release granular chlorine that is sold in it's own container/dispenser, ready to use and gradually and consistently supplies your pool water with chlorine.

  • Tablets: Chlorine tablets can be added to a basket-type floating chlorine dispenser and act in the same manner as a floater.

Beluga Tip: The ideal chlorine level in your pool water is 3 parts per million (ppm). Anything less than that, and your pool water isn’t really clean. Anything more than that is unnecessary and wasteful, and you need to dilute the water a little or hold off on adding chlorine for a while until the desired level is reached. When it comes to chlorine, there is such a thing as too much of a good thing.

You’ll also find two types available: stabilised and unstabilised chlorine.

Stabilised Chlorine If you have an outdoor pool, which most of us do, to prevent the sun from burning off the chlorine in the water, especially in our harsh South African climate you need stabilised chlorine. It has cyanuric acid also known as chlorine stabiliser or pool stabiliser, added to it.

The cyanuric acid protects the chlorine, so it stays in the water three to five times longer, making it more effective at keeping the pool clean so that you don’t have to replace the chlorine as often. This saves you money and time!

Beluga Tip: If the chlorine you buy doesn’t specifically say “stabilised” on the label, check the active ingredient. If it’s Trichloro-S-Triazinetrione or Trichlor, it’s stabilised. Yes, reading pool chemical labels is a thing…

Important: Again, there is such a thing as too much! Be careful of using stabilised chlorine for too long. If too much cyanuric acid builds up in your water, it will reduce the chlorine’s effectiveness and can even stall it all together called Chlorine Lock. If this happens, the only way to reduce the level is to dilute your pool water by removing some and replacing it with fresh water. Or, if there’s so much cyanuric acid that diluting the water won’t help, you may have to drain the pool altogether.

Unstablised Chlorine This type of chlorine is vulnerable to the sun’s ultraviolet rays, especially in South Africa. UV rays burn the chlorine out of the water, reducing its sanitising ability. This means you’ll have to add more chlorine to your pool more often, which means you’ll be spending more money and time.

So why would you ever want to use unstabilised chlorine? Well, if you have an indoor pool, you don’t have to worry about the sun eating up the chlorine. And if you are struggling with high cyanuric levels you don’t want to be using stabilised chlorine for a while which will be compounding the high levels even more.

It can also be used as pool shock, especially since you shock your pool at night (you do, don’t you?), so again, there’s no worry about the sun.

Beluga Tip: If the chlorine you buy doesn’t specifically say “unstabilised” on the label, check the active ingredient. If it’s Calcium Hypochlorite or simply Cal-Hypo, it’s unstabilised. This type of chlorine is most often available in granules rather than tablets.

Add the Cyanuric Acid Yourself Rather than using stabilised chlorine and risking the level of cyanuric acid building up too much, you can always opt use unstabilised chlorine and add cyanuric acid or stabiliser to the pool yourself. This gives you more control over the amount of cyanuric acid in your pool water.

Beluga Tip: The ideal cyanuric acid level in your pool water is between 30 and 50ppm.


During the oxidation process, chlorine dissipates and eventually becomes a waste product called chloramine. When you approach a pool and you smell that distinctive “pool smell,” it’s not that the chlorine level is too high (many people mistakenly believe this), it’s the chloramine, indicating that in fact your chlorine level is too low.

Chloramine is also what stings your eyes and dries your skin when you swim. It’s also not the best thing to breathe in.

To keep chloramines under control, you must add chlorine to your pool on a regular basis, according to how much it needs, which you’ll determine by testing your water (remember, your free chlorine level should be between 1 and 3ppm). And if the chloramines get really bad, and your pool really smells of chlorine, you’ll need to shock it to get rid of them.

The good thing is, you’ll be shocking your pool on a regular basis anyway (Right? Right!), so that will help manage chlorine and chloramine levels.

Salt Water Pools

Although this method of sanitisation has been around since the 1970s, this sanitiser system is fast becoming a popular alternative to the traditional chlorine pool in South Africa, mostly because it is more low maintenance and more cost effective in the long run. Salt water systems are also more gentle on the hair, skin and eyes as well as not being prone to chloramines.

However, while you may have been led to believe that all you need to do to maintain a salt water pool is throw in some salt every few weeks, it’s actually a bit more involved than that. Don’t fall victim to the mindset that low maintenance is no maintenance. Your pool water still needs to dance that tango to be well balanced so that the sanitiser can act effectively.

The most important thing to understand is that salt water pools are not actually chlorine free. A salt chlorinator creates the same kind of chlorine used in a chlorine pool by splitting the salt molecule (NaCl) into Sodium and Chloride, it does not balance your water. You’ll still need to test your water regularly, sometimes adding chemicals to balance it. These chemicals are the same ones you’d use in a chlorine pool.

Interestingly, salt water pools require higher levels of cyanuric acid or stabliser, so aim to keep the level between 70 and 80ppm, per most saltwater system manufacturers.

Beluga Tip: Always use good quality pool grade salt. The most important aspect of choosing pool salt is impurity levels, that is, minerals and metals contained in the salt. If you dump salt full of impurities into your pool water, you’ll spend time and money fighting imbalances, metals, or calcium carbonate build up.

Now that you have the basics of sanitisers down, let’s look at some of the other facets of balanced pool chemistry, and the pool chemicals that will help you achieve them.


Next to chlorine, this is probably the second most important partner in the tango. This pool chemical’s main job is to prevent pH from drastically moving up and down the scale by acting as a buffer, absorbing major changes to the water before they can affect the pH.

To keep alkalinity steady, keep a supply of alkalinity increaser, like Bicarbonate of Soda, on hand. If both your pH and alkalinity are low, alkalinity increaser, like Soda Ash, will raise both, another reason to adjust alkalinity first.

Alkalinity decreaser isn’t available as a separate pool chemical, so if your pH and alkalinity are both high a pH decreaser, like pool acid, will lower both. Lower the alkalinity first by adding pH decreaser with pool acid. Yes, this will also lower pH levels. Once the alkalinity is where it needs to be, then work on bringing the pH back up with pH increaser with Soda Ash.

This situation can be tricky to correct, and it may take several tries to get both levels back to normal, so make adjustments gradually to avoid throwing things even further out of sync.

Beluga Tip: The recommended alkalinity range in your pool water is 80ppm to 150ppm, with 120ppm being ideal.

Important: Because alkalinity protects pH, you must always adjust alkalinity first, then adjust pH, if necessary. Sometimes, getting alkalinity where it needs to be also brings pH in line.


If you remember from high school chemistry, pH is a measurement of whether a substance is acidic or alkaline. The scale ranges from 0 to 14, with 7 being neutral. Anything below 7 is acidic, and above 7 is alkaline.

Anything that enters your pool can affect the pH level. Rain, hail, dirt, leaves, people, dogs, anything.

For this reason, it’s important to stay on top of your pool’s pH level to make sure it stays within the optimal range.

Keep a supply of two pool chemicals on hand: pH increaser, like Soda Ash or Bicarbonate of Soda and pH decreaser, like Hydrochloric Acid also known as Muriatic Acid. You’ll likely use less decreaser because of how alkalinity is adjusted, but it’s good to keep some with your pool supplies just in case.

Beluga Tip: The ideal pH level in your pool water is 7.4 to 7.6. This creates an optimal environment for chlorine to do its job. It's also quite handy that the human eye pH is 7.4.


A measurement of how hard or soft your pool water is, calcium hardness may vary depending on where you live, and what water source you use to fill your pool. For example, borehole water is often higher in minerals, including calcium, than water that comes from a municipal source.

If the calcium level in your water is too low, it can lead to corrosion of your pool walls by drawing calcium out of the marbelite. Low levels will also cause scaling and corrosion of your pool equipment. This is remedied by adding Calcium Chloride Flakes.

If it’s too high, you may end up with cloudy water, which can be addressed by adding flocculant, clarifier, or a few other methods.

Beluga Tip: The ideal calcium hardness level in your pool water for Marbelite pools is 400ppm.

Important: High pH can lead to high calcium hardness. Before you try to address a high calcium level, adjust the pH first (after the alkalinity).


No matter how well you keep your pool chemistry balanced, it’s a good idea, no, it’s necessary, to shock your pool periodically especially when you’ve had a heavy downpour of rain or hail, a pool party with high bather load or if your pool gets that tell-tale green hue of an algae onslaught. Shocking is also sometimes referred to as superchlorinating the pool because all it means is you’re adding a high dose of chlorine to the pool all at once.

This is a good method for keeping the water clean, but it’s also a remedy for things like pool algae and certain mishaps that may occur in the pool, especially when small children swim.

Beluga Tip: Pool shock is made with unstabilised chlorine. It’ll get eaten up by the sun’s UV rays very quickly. So always shock your pool at night or dusk, and run the pump overnight to fully distribute it and allow it to dissipate.

Important: Products that contain calcium (like calcium hypochlorite shock or chlorine) can raise your pool’s calcium hardness level over time. If you use those products, keep a closer eye on calcium hardness levels so you can correct them before they become a problem.


If you only used chemicals to manage sanitiser, pH, alkalinity, and calcium hardness, you could theoretically keep your pool clean and healthy all season long.

But we don’t live in a perfect world, and there’ll be times when you need to help your pool fight things like algae, cloudiness, and staining. Luckily, you have a variety of specialised pool chemicals in your arsenal.


Your best defence against the dark arts that is algae, is sanitiser, especially chlorine. Keeping the chlorine level in your pool where it should be will keep algae at bay.

But things happen, water becomes unbalanced and algae sneaks in, undetected until you’ve got a full bloom growing and spreading through your pool like dementors, which is enough to make any resilient pool owner demented. Algaecide is your weapon of choice. Remember to check all your water parameters, there is a good chance your tangoing partners are out of sync as well because, remember that, in order for your sanitiser to be effective, everything needs to be balanced.

Clarifier & Flocculant

Why are these two separate pool chemicals? Don’t they do the same thing? Well, yes and no. There’s a major difference between pool clarifier and flocculant.

Cloudy pool water is usually caused by dead algae or mists of particles suspended in your pool water. The job of a coagulant agent, like clarifier or flocculant, is to clump these tiny particles into larger clumps so that they can be collected by your filter or flushed to waste. Now, clarifier and flocculant are two sides of the same coin. Both are types of coagulant agents that accomplish the same task using different routes.

The key differences are the time it takes for the reaction to take place and the extra elbow grease needed from you to finish the job. We will discuss the pros and cons and the best times to apply which chemical.

Clarifier Pros

  • Least amount of work for the user

  • Great for light cloudiness and superfine silt


  • Takes several days to get the desired result

  • Pool clarifier is a mild coagulating agent that boosts your filter’s cleaning capabilities by clumping small dirt particles into larger particles your filter media can trap. Clarifier requires that your pump and filter are run continuously for at least the first 24 hours for optimal results.

Clarifier is a milder chemical than flocculant making for a slower work rate. Your pool’s reaction to the clarifier may take a couple of days before you see the results. So, if you are needing a quick fix for a pool party only hours away, clarifier will not be the choice for you.

Clarifier is the ideal choice for mild cloudiness or a regular part of a cleaning regimen to give your water that extra sparkle.

Flocculant Pros

  • Shows results within a few hours

  • Very effective


  • Requires vacuuming on waste (cannot be used with an automatic pool cleaner)

  • Water wastage

Flocculant’s coagulation process is basically a supercharged version of a clarifier. But instead of relying on a pool filter to do the cleaning, it requires vacuuming. Flocculant clumps the dirt into large clots, so large that they no longer float, dropping all the dirt to the pool floor where you can then vacuum to waste. Your pool should show marked improvement within a few hours of its application, making it ideal for procrastinators cleaning just before a pool party.

Flocculant can be used for mild cases of cloudiness all the way up to murky. However, we suggest it as a last resort, because you must manually vacuum it to waste. You can lose a good bit of water while cleaning the pool.

Important: Flocculant should never come in contact with your sand filter as the clumping agent can cause havoc. Flocculant is only suggested for use with filters with bypass options, i.e. sand filters with a multiport valve that can be turned from 'circulate' to 'waste'.

So which is best for you? Clarifier is best suited for basic maintenance, and picking up straggling silt your filter just can’t seem to catch. Flocculant is best for more severe cases. Flocculant shows results within a few hours, making it great for cleaning in crunch time.

Metal Remover

If your water contains metals such as iron and copper, you may see some rust-coloured or green pool stains. You’ll need to clean the pool to get rid of the stains, but you can prevent them from reoccurring by using a metal remover.

This pool chemical attaches itself to metal particles in the water so they can’t settle on surfaces and stain them. If you use borehole water to fill your pool, you may want to keep some metal remover close by and have your pool water professionally tested at your local pool store so that you can take the necessary precautionary action.


Knowing which pool chemicals to use when is only half the battle. There’s no way to know what the chemical levels are and whether you need to add or remove anything without checking your parameters.

You’ll probably test your pool more often than you do anything else to it. Before you add chemicals? Test it. After you add chemicals? Test it. After a rainstorm or big pool party with lots of swimmers? Test, test, test!

The quickest and easiest way to test your pool water is with test strips. If you want a more comprehensive and accurate reading, use a liquid test kit. If you’re into tech and gadgets and can afford them, you can get a digital water testing kit.

And at least once every few months, take a pool water sample to your local pool store and have them test it for you with their even more comprehensive and accurate testing abilities.


Hey, no one ever said having a pool would be easy, but it also doesn’t have to be difficult. Knowledge and the right pool chemicals make all the difference in the world.

Don’t let your pool intimidate you. You manage your pool, not the other way around.

Just remember that no one expects you to know everything overnight. Even more important than having the right tools is knowing where to find the right information. And you’ve already done that, so you’re on your way!

Happy Tangoing!

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