What Chemicals Do You Need for a Swimming Pool?

Owning a swimming pool is a wonderful way to enjoy leisurely exercise and family fun in the back garden. It’s a great way to cool down and enjoy the summer by relaxing with a book or having pool parties and barbeques.

But owning a swimming pool also comes with various other activities and responsibilities. It is only natural to be confused when first encountering swimming pool chemistry.

This guide will help simplify the initial bewilderment involved with balancing out your pool, which is an easy way to ensure crystal clear water!

Here at 1st Direct Pools, we supply the appropriate chemicals and products involved with maintaining a clean, safe swimming pool. You can find chlorine tablets, swimming pool covers and much more on our website.

What Do Swimming Pool Chemicals Do?


If untreated, the swimming pool can easily become comparable to a pond. The water can become an uninviting and unsterile environment that welcomes algae growth, which will turn the pool various shades of green.

The water may also become corrosive; this can be indicated by the water taking on a cloudy appearance. It may even start to harbour harmful bacteria.

Balancing out the water chemistry of your pool will encourage a healthy, clean pool for you and others to enjoy. The chemicals create the perfect environment for the sanitising chemical, such as chlorine, to effectively sterilise the water.



Pool water chemistry essentially revolves around supporting chlorine to do its job. It is a crucial component in maintaining the condition of your pool as it destroys and prevents algae from forming.

The recommended value for chlorine in a swimming pool is 1-3ppm (parts per million)

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Tablets, Granules or Liquid?

It’s fairly easy to treat a pool when using chlorine, but it can be slightly confusing when choosing from the various types. Chlorine can be found in tablet, granule and liquid forms.

The most popular option and easiest to administer is tablets. These are often placed in a dispenser that will float in the pool, meaning chlorine will slowly be added to the water over an extended period of time.

Granules can be added to the water directly, but it’s highly recommended that they should initially be mixed with water to form a solution before distributing into the pool water.

Liquid chlorine provides a simple solution for maintaining a clean swimming pool. However, it is primarily used for industrial swimming pools, where a substantial amount is required.

For the vast majority of swimming pools, tablets are recommended.

A football floating in water


Effectively, bromine does the same job as chlorine, only in a different way. You will not require bromine if you have used chlorine and vice-versa.

Bromine will often cost a bit more than chlorine, hence the popularity of the latter. However, that’s not to say that bromine doesn’t have its unique advantages.

Chlorine is an effective cleaner, but it can cause irritation for those with sensitive skin. Due to bromine’s different nature when reacting with water, it can cause less irritation.

It is also less susceptible to evaporation in comparison to chlorine, making it a popular option for hot tubs and heated pools.

Bromine requires a reading of 2.5-4 ppm for swimming pools. Similar to chlorine, bromine is available in an array of forms but tablets are recommended.

It’s important to note that in comparison to chlorine, bromine tablets will dissolve at a slower rate; this is an important factor to consider when balancing and testing your pool water.

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Shock Treatment


Shock treatments play an important role in the general maintenance and cleanliness of your swimming pool. These products are highly-concentrated versions of chlorine or bromine.

If your sanitising chemical levels have depleted substantially, shock treatment will often redeem the issue. Shock treatments are also effective in removing any algae or bacteria that is harbouring within the water.

Shock treatment should be used after periods of inactivity, even when the water appears to be crystal clear. It is essential to treat the dormant water before using the pool.

Unlike chlorine’s standard counterpart, chlorine shock (which is also known as hypochlorite) will always come in granular or liquid form.

When using these products, the water’s balance can become unstable and again be deemed as unsafe. Therefore, the water will need to be tested and re-balanced again before use.

pH Increaser


The pH level of a pool is also essential, as it will measure the acidity of the water. If the pH falls below the necessary level, the water may cause skin and eye irritation.

The most commonly used pH Increaser is known as Soda ash or Sodium Carbonate. These products are often available in powder form and are easy to use.

Two people’s legs sticking out of a pool

pH Reducer


pH reducer works along the same lines as pH increaser, just in a different direction.

pH reducer should be utilised when the water’s pH level becomes too high. When the water’s pH level is too high, the chlorine effectiveness will be drastically reduced.

pH reducers are often known as Dry Acid and Sodium Bisulfate. These products are commonly in the form of a powder and easy to administer.

Total Alkalinity


Alkalinity is sometimes referred to as Total Alkalinity or TA. Alkalinity is another element to consider when balancing out your pool water, as it will ensure healthy and safe swimming water.

The alkalinity of a pool will also affect the chemical balance of the water. The desired range of alkalinity is 80-120ppm.

If the reading is outside of the required range, the pH balance will be affected which may lead to erratic pH readings. An affected pH balance will then go on to unbalance other chemical readings of the pool.

Alkalinity Increasers

Alkalinity Increasers are sometimes referred to as TA Plus; these often consist of sodium bicarbonate, otherwise known as baking soda.

The Alkalinity Increaser is available in a powder-based form and is used in a similar way to pH adjusters.

The water will require a water test after as the Alkalinity Increaser can impact the pH levels.

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Alkalinity Reducer

Due to pH and Alkalinity being linked, it is possible to use a pH reducer such as sodium bisulfate to also reduce the total alkalinity.

Another option for reducing the alkalinity is Muriatic Acid, although this can often be hazardous. It is much easier to use a pH reducer for this task.

Water dispercing out of a pool fountain

Calcium Hardness


Calcium hardness is another chemical measurement that will need regular readings.

This measurement will demonstrate how much calcium is in the pool – too much will result in build-up, while too little can cause the water to erode the walls and metal of the pool.

Calcium chloride is the most common chemical when treating calcium hardness. This chemical is often available in a granular form, and this will need to be added to the water when the calcium hardness reading becomes too low.

Unfortunately, if the calcium hardness becomes too high there are no quick-fix solutions or chemicals available to reduce the calcium of the water. The pool may need to be drained, replenished with clean water and then rebalanced.

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Chlorine Stabiliser


Sometimes known as a conditioner, a chlorine stabiliser is not necessarily essential, but it can be helpful for certain swimming pools. Chlorine can evaporate if frequently exposed to the harmful UV rays from sunlight.

Chlorine stabilisers help to prevent this by using cyanuric acid which will block the UV rays. For most UK pools, cyanuric acid won’t be required. It is worth noting that using a chlorine stabiliser is not a substitute for testing the chlorine, pH or alkalinity levels.

If the pool becomes exposed to a lot of sunlight, it is recommended to regularly test the water for any alarming reductions in chlorine levels. If the readings indicate this, then the use of chlorine stabilisers can provide a solution.



Clarifiers are designed to polish the water, which will create a crystal clear pool.

There are many different swimming pool clarifiers available. These work by causing the tiny pieces of debris in the pool to clump together, helping the pool’s filteration system to extract them.

Similar to stabilisers, clarifiers make a nice addition to swimming pool setups. However, they are not a substitute for regular maintenance.

If your pool requires a deep clean, depending on the nature of the dirt, you should consider either vacuuming your pool or using a shock treatment.


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A woman flicking her hair in a pool

If you are in need of any advice, you can contact our team at 1st Direct Pools who will be more than happy to help, or you can check out our blog for more information.

Our website has a range of products available that can provide a solution to any issues you may encounter with your swimming pool.