The use of sanitisers in spa and swimming pool water treatment

In a recent blog post, we outlined three essential components of spa and swimming pool water treatment: sanitise, balance, clean. In this blog post, we explore the role of sanitising chemicals.

Sanitisers are the most important group of chemicals used for treating your spa or swimming pool. Their job is to quickly kill any bacteria that get into the water so that they cannot multiply and cause infections in users.

Bacteria in spas and swimming pools

Bacterial growth is the primary cause for concern when it comes to swimming pool and spa safety. The main bacteria to be aware of include:

E.coli - E.coli can respond to environmental signals such as chemicals, pH and temperature and can cause symptoms such as diarrhoea and visceral disturbance.

Pseudomonas - Pseudomonas is a common bacteria found in humans. When people become infected with pseudomonas they can cause infections such as inflammation and sepsis. If it gets into the lungs, urinary tract or kidneys, it can be fatal.

Legionella - Legionella bacteria grow in water and if people inhale small droplets of infected water it can lead to the potentially deadly Legionnaires’ disease.

Shigella - Shigella are bacteria that can infect the digestive tract and cause a wide range of symptoms from diarrhoea, cramping, vomiting and nausea, to more serious illnesses.

Spa and swimming pool operators are required to test for bacteria regularly.

How sanitising chemicals prevent and kill bacteria

Chlorine and bromine are the most commonly used sanitisers in spa and swimming pool water treatment.


Chlorine, which typically comes in liquid or solid granular form, can kill bacteria such as E.coli in under a minute. Chlorine levels of between 3.0 to 5.0mg/l are sufficient to maintain healthy, clean water. A well managed chlorine-treated swimming pool or spa will have no odour and levels of chloramines (combined chlorine) of less than 0.5mg/l. Combined chlorine is created as a result of the reaction between free chlorine and organic matter in the pool.


Bromine is similar to chlorine in its effectiveness as a sanitiser for swimming pools. However, it can be more popular in spa pools because it does not give off the odour associated with chlorine and can be more effective in the 7.2 - 7.6 pH range normally seen in a spa pool. Bromine tablets are dosed into the water via a feeder and are slow releasing.

Other types of sanitisers include:


Superchlorination or ‘pool shocking’ can be used to kill the build-up of combined chlorine and anything else floating in the pool that doesn’t belong there. Calcium Hypochlorite can be used as a ‘shock’ treatment. It is supplied as a powder and dissolved before being added to the water. Recommended use is 20oom for 2.5 hours.

Non-Chlorine Shock

Non-Chlorine Shock is not a sanitiser in its own right, but it can be used to enhance the effectiveness of the primary sanitiser by freeing up chlorine that has become attached to organic matter and allowing it to continue to oxidise bacteria.

Chlorine Dioxide

Chlorine Dioxide is a fast-dissolving product that can also be used to ‘shock’ the pool. It comes in a convenient effervescent tablet form and can be used to supplement the sanitiser regime through periodic addition.


Sanitisers play a key role in spa and swimming pool water treatment. They keep the water safe for users by preventing and killing bacteria. But this is just one part of the equation - the water must also be clean and balanced. In our next blog post, we look at the role of water balancing chemicals in spa and swimming pool water treatment.

For a complete list of B & V's sanitising chemicals, click here. Or get in touch with our technical team for advice on the right products for you.

Shane Lynch

Shane Lynch

Shane Lynch has been in the Water Treatment industry for 15 years, specialising previously in industrial water treatment applications. He is now working as a sales and support consultant for the B & V Chemicals team, offering customers technical and specialist product support.

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Supply Partners

HuwaSan specialise in the production and distribution of chemicals for water treatment. B & V Chemicals are water treatment supply partners in the UK.