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The Complete Guide to Pool Chemistry in 2021

Pools are complex systems that can cause headaches and tears of frustration when you need to keep them clean without any help. Some of the most complex systems have been created to help decrease the number of chemicals you need to add, however, you will still need to add some chemicals as the levels start changing.

You will need to check the chlorine and Ph levels of your pool each day, adding chlorine, acid, or alkalinity up as your readings indicate. The simple truth is that any other extreme chemical like flocculent, algaecide, or metal remover only when something has gone extremely wrong with the water.

These are only the basic things and knowing that you have to do them is not the same as actually doing them. Many people have some strange results when they are doing their testing and need to add a few chemicals that most won’t be aware of. Knowing what to check daily with your pool, and when to see that a test result is incorrect will allow you to save hours trying to fix it later.

What are the five important chemicals to check?

Many chemicals will affect the color, feel, and smell of your pool water with most of these being balanced each day. Some of the best pools in the world will use these and are constantly tested by their maintenance workers to ensure that they are perfectly balanced.

Many times, the only maintenance you will have to do for many years on your pool will just be to check the balance of each of these five basic chemicals. Having the perfect balance most of the time with these will ensure that your pool won’t turn green the day after it has rained, a quick boost will keep it blue over a vacation, and leaves won’t shock your pool system into complete chaos.

Check PH Levels

Many people think that Ph is the easiest part of the pool to understand, however, it can easily be the most complicated part to have perfectly balanced. Some of the most dangerous pool water can be created when people mistakenly think Ph is focused purely on the acidity of the water, however, this is not true.

Checking the Ph is more focused on checking to see if the water is turning into a base, which will be reading higher than 7.8 on the testing kit. As the Ph levels of water raise it moves away from being balanced or acidic, becoming more like a base chemical. This can easily start burning skin, eyes, and nostrils as pool water can easily turn base-like through natural means.

Balance Chlorine Daily

Chlorine is one of those chemicals that is simply amazing and scary at the same time, being one of the things that can easily cause death and destruction. Or with pool water and drinking water, create something that is perfectly clean to swim in or drink. Chlorine is the most important chemical you will be adding to your pool daily and you should check the chlorine levels every second day.

Chlorine kills algae, bacteria, and many other dangerous naturally occurring things that you do not want in your pool. Further, many chlorine solutions have a few additives that will keep the rest of your pool clean and balanced. The biggest challenge you will face with chlorine is adding too much, or the sun burning away the chlorine that you have added.

Alkalinity Needs to be Stable

There is a prevailing misconception that alkalinity is the opposite of acid being thrown into your pool when it is an entirely different chemical that you need to add. Usually only needing to be adjusted once per season it is a chemical that will easily start causing your pool to become slightly wrong when it is not perfectly balanced.

Alkalinity can easily be tested and to fix it will usually just involve throwing in some granulated alkalinity up. Not having balanced alkalinity will cause many of your other chemicals to become unbalanced as the water is unable to be adjusted with ease, it will also start causing an uncomfortable feeling on the skin. Usually resulting in water that feels hard to the touch, causing people to not want to swim in the water.

Calcium Hardness Levels

Calcium is one of the fundamental chemicals that will be in your pool water, which when it is not present the water will be hard to deal with. When it is too much you will also have a buildup of chemicals and stains across your pool. Many people that prefer to fill their pools through boreholes find that their calcium levels are always too high.

To balance calcium is quite easy, you will need to drain out a significant amount of water, usually then only refilling the pool with clean tap water. This allows your pool water to easily and comfortably become calcium-free, and much easier to handle as you are adding other chemicals to the mix.

Negate Acidic Water

When you are working on balancing everything else in the pool you may need to add a few liters of acid to negate something else in the pool. Usually, this is done on the regular when you are using borehole water or you are in a rainy area of the world, both of these can cause your water to turn green and to need acid.

However, if you add too much acid to a pool then the water will turn acidic, long before it starts being harmful to humans the water will start eating on the lining of your pool. This causes damage that may need to be repainted as your pool ages, there is only one way to counteract this acidity. You need to add more water to the pool, usually, people will remove some water as well.

Why do you need to check chemicals?

It is one of the most tedious things that you will need to do at least once a week if you don’t have someone that will be cleaning your pool. You need to test the water constantly, checking to see that each chemical is at the right level. Usually, people have quick test strips to do this, but even this can be quite a drag to do when you have to do it constantly.

This process leaves many people wondering why they are constantly testing, and the simple answer is that testing constantly is the quickest way to figure out what is wrong. Even a green pool can have fifty different reasons why the water has turned green. By testing the water, you will immediately know which chemicals you need to add in right away to start counteracting everything.

Many people become sufficient enough with their pools to automatically know what to add and when to add it. Knowing that after rain they will add a few liters of acid and two or three scoops of chlorine. However, you will see that even pool owners that have been living with their pool their whole lives will do regular testing.

How do you measure the levels of the chemicals?

Knowing that you need to test the pool regularly is just the first step, many people are not aware of all the ways you can easily test the water for everything. There are many ways to test, but pool owners and lovers have narrowed it down to three specific types of tests that we know will always deliver accurate results.

Pool testers are constantly being updated and perfected, as some of the chemicals that are needed in different countries are not measured on every testing kit. Knowing what each testing kit is generally used for and why owners are using them will greatly relieve your stress when choosing your pool testing kit.

Using quick check Strips

One of the most popular testing kits to use is the quick test strips that you only need to dip in the water, usually then comparing the colors of the strips to the back of the box they came in. Using these will give you a good idea of what the chemicals in the pool are doing and what you will be needing to throw in before heading off to bed.

It is important to remember that these strips can only give you a rough idea of what to do and what is happening in the pool. Using these exclusively usually leads to an imbalance of some chemical that requires more in-depth testing to get perfect. Testing strips should always be used alongside a full testing kit, you should use the testing strips every second day, while using the testing kit once every 7 to 14 days.

Use a full pool testing kit

A full testing kit is hard to explain and there are many different versions of them on the market, but the best types will have a testing kit with two vials on them, accompanied by a mixture of four droppers. These are testers that will tell you more or less exactly what the levels of your pool are and how much of each chemical you will need to add.

Full testing kits can take a longer time to test the pool as you will need to add specific drops of testing chemicals. Fortunately, these testing kits last quite a long time even with regular testing and you will only need to replace the strips regularly. Using the testing kit to figure out how much of each chemical you need to add will usually allow your pool to stay sparkly clean.

The modern checker

This is a newer addition to the world of pool and many upper-class pool owners have started installing them into their pools. Digital chemical checkers usually only need to be topped up with chemicals once every few years and will constantly give you an updated feed of the chemical levels of your pool.

When you are using one of these systems, especially one created in 2021, you will have an app on your phone that automatically updates and will give you exact readouts about how much you need to add to your pool. They are gaining traction because they take a lot of work out of the pool chemical balancing system, usually making an arduous job into a simple press of a button.

Why do you need to check on chemicals regularly?

If you are a first-time pool owner you may quickly get discouraged by the thought of testing your water every few days, usually thinking that it is fine to only check once a week. Not checking the water on the regular is a quick way to create a pool system that is neither happy nor ready for you to swim in.

By not checking every day you will allow a lot of growth to suddenly start-up in your swimming pool, with many owners learning the hard way that once algae have started forming in the pool it can feel impossible to clean. You need to check the chemicals regularly to ensure that they are there to stop any algae to grow before it has been given the chance to grow.

If you have left testing off for too long and things are growing in the pool you will have to face the challenge of doing a shock treatment. A process that can easily last a week as you are sucking up all the dead leaves and algae that have now settled at the bottom of your pool. Sometimes doing a little bit of constant work can save you from doing a lot of hard work down the line.  

What are the more extreme chemicals you should use?

You may be wondering why the pool aisle is so large when there only seems to be five chemicals that you need to check on. However, this is not the truth and the full suite of chemicals that can be used to keep your pool clear and sparkly is hard to count. There are many chemicals that you can add to get stubborn stains out, clean hard to reach places or even just add a bit of sparkle.

Please remember that if you find yourself using these chemicals every single swimming season, or even more than once in a season, you will have to check on the full system. It usually shows that there is a leak somewhere or that you need to replace some key parts to ensure that everything is still working as well as it should.

  • Sand cleaner: A chemical process that can take quite a while to do and will cause you to have a few headaches when you need to do it. Sometimes you may notice that the water only turns green when you are using the filter, this means something is growing in the sand filter. You can try to use a sand cleaner that will clean the entire pipe system, or just replace all the sand in the filter.
  • Flocculant: Sometimes you win the battle of the algae and you kill everything growing in your pool using only chlorine and acid. Other times you wake up one morning and the entire pool has become a murky mess. Either way, you add flocculant to the pool when you want the water to become entirely clean and shiny, with a thick layer of things at the bottom of the pool. After using flocculant, you will have to sweep everything up from the floor of the pool and using the waste function to get it all out.
  • Algaecide: Algaecide come in three flavors, green, black, of an all-in-one that will usually kill everything living in your swimming pool, they also have a slightly sweet smell. Using algaecide is an easy way to have your pool become extremely clean but slightly murky as there are many dead algae now floating in your pool.
  • Metal remover: It is said that you will only use a metal remover when you know you will need it, which is a slightly true statement. If you are seeing small or large parts of your pool suddenly chancing color it is usually metal gathering up. This can easily and usually does lead to your pool floor being stained, metal remover will help to loosen these and allow you to vacuum out the excessive metals that are floating in the water.
  • Stabilizer: A chemical that should only be added once or twice in a swimming season stabilizer is there to help the chlorine in your pool survive the sunlight. This chemical is only used in hotter countries where the sun can reach a temperature hot enough to break down the chlorine in the water. If you have an indoor pool it may never be needed to add a stabilizer into your pool.
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Written by Ferdi Vol
Ferdi Vol is a pool and hot tub owner who has been working in this industry for over 5 years. He has learned all the ins and outs of maintaining pools and hot tubs, as well as how to privately own one. Ferdi Vol is also passionate about blogging, researching topics that he shares with his readers online via this blog.
About Ferdi Vol
About Pool Uncle
Pool Uncle is a blog that focuses on helping pool and hot tub owners get the right tools, maintain their pools and hot tubs, and learn about how to care for them. It provides readers with all of the information they need to keep their pools clean, safe, and looking great. The website also publishes original articles about pool maintenance topics such as filtration systems or algae prevention techniques.
About the Author
Ferdi Vol has been in the swimming pool and hot tub as an owner for over 5 years. His experience ranges from owning a pools and hot tubs and maintaining them. He’s learned about pumps, filters, chemicals, cleaning products, treatment systems… you name it!
About Ferdi Vol
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