Essential Guide to Using Spa Chemicals  

by Pool Builders on 10-11-2012 in Articles

Even though spas are much smaller than swimming pools, they require the same principles of care and cleaning. Heated water in particular is the perfect breeding ground for bacteria, so it must always be properly sanitised and filtered to provide safe bathing conditions as well as to prevent the water from becoming cloudy.

In addition, unlike swimming pools, the water in your spa must be changed on a regular basis, so it will need to be drained and refilled.

The following guide will outline the sanitizing agents you can choose from to effectively clean the water in your spa, hot tub or swimming pool.

Summary of Key Cleaning Materials

Here is a list of the main solutions used for water sanitization:

€ Sanitizers - a blanket terms for agents which destroy harmful bacteria and other contaminants in the water. Chlorine and bromine are the most common chemicals used for this.

€ Chlorine Stabiliser - prevents unnecessary loss of chlorine so that it works more effectively as a sanitizer.

€ Algaecide - kills and prevents the growth of unwanted algae.

€ Soda Ash (sodium carbonate) - also called pH Plus, this is used to increase the pH level of the spa water.

€ Sodium Bisulphate - also called pH Minus, this is used to decrease pH levels.

€ Filter Aids / Flocculants / Clarifiers - these help remove debris from your spa.

Understanding Sanitization

It is extremely important to disinfect (sanitize) your spa to prevent the growth of contaminants such as bacteria and algae. This involves using chemicals to neutralise these harmful micro-organisms as well as filtration to remove larger pollutants and debris.

You will also need to conduct regular testing of your spa water using a specialised kit to maintain the right balance of its pH levels - this is a crucial since correct pH is essential to the safety of bathers and the spa structure itself.

There are different types of testers available:

€ Test Strips (Litmus paper) - the simplest and quickest means of testing your spa for chlorine and pH levels.

€ Liquid Reagent - this type of test kit needs the exact amount of reagent to work effectively.

€ Test Tablets - many people prefer these kits as they offer simple, affordable, accurate analysis of spa or pool water.

Most Common Sanitising Chemicals

The most commonly used methods of sanitization are chlorine and bromine. Both are from the halogen family, meaning they have the capability to efficiently rid the spa of contaminants. They also have a residual effect, meaning they continue acting on the water long after they have been added. In addition, these chemicals are a popular choice since they're affordable and easy to use (although some basic safety measures need to be followed, such as wearing gloves when handling them).

There are many types of chlorine releasing compounds and these tend to be used most often for sanitisation. Many women however complain about the smell of chlorine attaching itself to their hair, so in recent years bromine has risen in popularity amongst spa and hot tub owners.

Chlorine in particular tends to break down rapidly in sunlight, so to extend its sanitising ability it can be supplemented with chlorine stabilisers such as cynuric acid, which can prolong the residual half-life by as much as four to six times more than normal.

It's very important when using these chemicals to maintain them at the recommended levels, since weak amounts will obviously reduce their sanitising effectiveness, while overly high amounts can lead to unpleasant side effects such as eye and skin irritations.

Alternative Sanitizers

Some people find sanitising chemicals to be too harsh, so they prefer more natural alternatives to chlorine or bromine:


Ozone is generated by nature, particularly thunder storms, but it can also be synthesised artificially to kill bacteria in air or water. In fact, ozone is 300 times more effective than chlorine as a sanitizer.

UV Filtration

Ultraviolet light has a special irradiating effect which actively neutralises bacteria in water.

I must mention however that the downside of both of these methods is that they do not have residual properties, meaning they won't continue to disinfect the spa or pool water when not activated. For this reason you will need to continue to use low levels of chlorine or bromine to tackle the constant growth of bacteria in water.


It is absolutely vital to perform correct, consistent sanitisation and maintenance of your spa, hot tub or swimming pool in order to keep it (not to mention bathers) free from harm. Using the above information on spa chemicals and other sanitising methods, you will be well on your way to making the right choices for your needs.

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