The Ultimate Guide to Balancing Chemicals in your Hot Tub


Balancing Chemicals in your Hot Tub is key to clean, crystal clear and problem free water. In this blog post we are going to look at what a balanced set of chemicals look like and how we can resolve some common problems.

Before we start, I must point out that this is written from personal experience, I am not affiliated to BISHTA. BISHTA is the trade association that represents the British and Irish Hot Tub and Swim Spa Industry. Nor am I professionally chemically trained. The is advice only from personal experience so please do with it what you will at your own peril!

Why do we need Chemicals in a Hot Tub?

We need chemicals in a hot tub primarily to kill bacteria that could breed in a warm damp environment. By using a combination of chemicals we are able to remove the bacteria which could be harmful to us from our Hot Tubs and control the water for longer.

What Chemicals do I need for my Hot Tub?

When we are talking about Hot Tub chemicals, we are really talking about 6 things

  • Sanitiser
  • pH Increaser
  • pH Decreaser
  • Total Alkalinity Increaser
  • Anti Foam
  • Clarifier (optional)

Let’s have a look at what each of them does.


Sanitiser is the main chemical that is going to kill bacteria in your Hot Tub. There are two main choices here. You can either opt for Bromine or you can choose Chlorine. I am going to write an article at some point about the difference and pros and cons between the two, but for this article, I am going to concentrate on Chlorine as that is what I use in my own tub and it is more popular.

Just as a side note, Bromine is particularly good if you have sensitive skin or react to Chlorine. It means you can still enjoy the Hot Tub without the associated skin complaints!

Bromine is a sanitizer, oxidizer, and algicide that is used in swimming pools and Hot Tubs. In its original state, bromine is a reddish brown liquid, but for pools, it can be found in tablet, granular, stick, and liquid sanitation products (though you would never use pure elemental bromine in a pool or spa). Any liquid bromine products that you may find are diluted with water and other chemicals for safe handling and better performance.

“Bromine” isn’t true bromine, but the name is used to describe any chemical that releases hypobromous acid into the water. This takes place in two ways:

  • The two-part system consists of sodium bromine activated by an oxidizer and is typically used in smaller volumes of water (spas).
  • The solid, dissolvable form of bromine (tablets, granules, etc.) is formed when bromine is bound to an organic molecule.

What are the Pros and Cons of Chlorine?

A chlorine purification system is the standard method of sanitizing your pool water. Chlorine is added directly to the water to kill bacteria, viruses, and algae. Using chlorine purification system requires the pool owner to test the PH of the water, measure out the correct balance of chemicals, and add them to the water. This system is done routinely by the pool owner as part of their routine pool maintenance.

Chlorine Pros

  • Chlorine is a powerful oxidizing agent thereby getting rid of a lot of bacteria in water.
  • Chlorine is commercially available
  • Chlorine is very economical

Chlorine Cons

  • Chlorine does not exterminate all bacteria. Complex microorganisms are known to become dormant in the presence of chlorine but not exactly killed
  • Chlorine is not green. It is harmful to the environment.
  • Commercially available chlorine (Hypo) disintegrates into Chlorine gas rapidly when exposed
  • Super-chlorination poses danger to humans over a period of time
  • Downstream water treatment systems like Resins, RO/UF membranes may be damaged by excessive chlorine at inlet.

What are the Pros and Cons of Bromine?


  • Does not give off a strong smell
  • Gentler on the eyes than chlorine
  • Effective disinfectant and algicide
  • Acts as an oxidizer
  • Great for sanitizing spas and hot tubs
  • Works with vinyl liner, concrete, and fiberglass pools


  • More expensive than chlorine
  • Less oxidation power than chlorine
  • Not suitable for those with chlorine allergy
  • Does not work as well when exposed to sunlight

Are there any Alternatives to Chlorine or Bromine?

  • Minerals – silver and copper minerals to be exact which can be used to used to purify spa and hot tub water. It’s been around for over 20 years, so it’s not new in the world of spas and hot tubs, and copper and silver ions have been purifying water for eons, so it’s not new to the world. That said, I know very little about this at all so I’m going to leave this one here and you can google around the topic if you so wish.
  • Salt System – Any hot tub can be a saltwater hot tub with the addition of a salt chlorine generator. Instead of adding chemicals directly to your hot tub, you add salt (about two pounds per 100 gallons of water), which dissolves to produce natural chlorine that’s needed to keep your hot tub clean.Because you’ll need to purchase the salt chlorine generator, saltwater hot tub prices may be higher initially, but the maintenance of saltwater tubs is generally cheaper than the maintenance of traditional hot tubs.


pH Increaser & pH Decreaser

Before we look at increasing or decreasing pH levels, what is pH? pH is the measurement of the acidity or alkalinity of the water in your hot tub. It is a scale from 0-14 with regular water being ‘neutral’ and as you would expect, coming in at the middle of the scale as a 7. The more acidic your Hot Tub water is, the lower the pH value. The more alkalis your Hot Tub is, the higher the value.


Why is this important? Firstly, if the water is too acidic, it is going to corrode your Hot Tub parts which is going to be costly in the long run. If you are going to corrode the heater element in the Spa Pack, this is going to cost £200-300 ($400-500). If there is not enough acidity, the water could cause stains in your Hot Tub due to mineral scaling. It can also cause health problems so it is kind of important to get it right.

One of the main things that the pH determines his how well the sanitiser works. For the ideal setup, your Hot Tub needs to between a pH of 7.2-7.6


Total Alkalinity Increaser

This is where things can get a little confusing. What Total Alkalinity (TA) is really the overall position of the alkalinity of the water. This also affect the hardness of the water. Why is this important. Well, if you cannot stabilise the TA of the Hot Tub then you will find it difficult to move the pH of the water up or down to balance. If your Hot Tub is out of balance, then the sanitiser doesn’t work effectively, bacteria and the nasties start. So it is important.

One of the things I didn’t realise was that you tent to buy TA Plus (total alkalinity increaser) but you dont buy “TA Down”. It’s a bit confusing and we will cover the scenarios further into this article. However, if you need to reduce the TA of the Hot Tub which should be at 80-120 ppm (parts per million you use pH reducer to bring it down, then you take just the pH back up to the correct level with pH Increaser. Complicated? It’s not really, just read the paragraph again if you are still not quite sure.


What do I need to test the Chemicals in my Hot Tub?

Testing your tub on a regular (weekly) basis is essential so I would advise on investing in a digital tester. They are not too expensive but save a lot of guesswork.

If you don’t want to go down the electronic testing, some simple dip strips will do the job.

Anti Foam (optional)

Anti Foam is also an optional Chemical but it is one that I use. Have you ever seen a Hot Tub that is full of foam on the top? The foam is caused by detergent usually coming from the clothes of the bathers in the Tub. If the Hot Tub chemistry is not quite balanced, then the detergent can react with the water and cause excess foam.

What Anti Foam does in a simplistic way is kind of like when you put a bar of soap in a bath full of bubbles, the bubbles disappear. This is the job of Anti-Foam does.

This should be however a short term fix to the ‘problem’ which is more than likely chemicals slightly out of balance. We’ll look at this later in this post.

Clarifier (optional)

Water Clarifier. This I have marked as optional as it is not really needed but it makes the water look good. If your water has a bit of a murkiness to it because there is small drops of matter suspended in the water, this can help. What Clarifier does is that it helps the particles of matter combine into larger particles that your filter can then trap and keep out of your water.

If the particles are too small, they will pass through the filter and can cause your water to not look that appealing. Add some clarifier whilst the jets are going, a good squirt usually does it and you will soon see the gleaming sparkly incising water once again.

What is the Perfect “Balance” of Chemicals in my Hot Tub?

According to the experts the chemicals should sit between the following readings that I have summarised in an Infographic;


This blog is somewhere where I share my own experiences so what I will say is that I tend to run a little higher than recommended on Chlorine.

I’m sure there are chemically trained experts out there that would disagree, but I have found no harm in keeping the chlorine a bit higher than the recommended readings.

At no point have I or any of the rest of my family had any adverse effect but it does mean that I can be sure that no “bugs or bacteria” is lingering in the tub.

What you will find is that over time you will get used to the amount of Chlorine you need to add. For my 2700 litres (650 gallons) I add once a week 5 x 20g in tablet form to the filter. I drop this in on a Wednesday knowing in will be using the Tub on a Friday.

If it has been a “big weekend” for the Tub with lots of guests, I’ll drop a few extra tablets in on a Sunday night.

Regular testing and checking is vital to clean, clear, disease free water. It’s fun. Believe it or not, I find it quite self fulfilling when measuring the levels to make sure they are correct.

Even more so when the water is crystal clear (as it is today and most days to be honest) – means I am doing something right.

I’ve had the tub for a 18 months now, and (touch wood) no issues with people’s health so again, in my head I am winning 😉

What I will say is that excluding chlorine which I am a little heavy on, the rest I stick to the proverbial book. If you don’t you get foam, murkiness and things do not look good.

These levels are there for a reason so stick to them.

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What Happens if pH is not right in my Hot Tub?

High pH Readings Low pH Readings
Poor Sanitizer Efficiency Poor Sanitizer Efficiency
Cloudy Water Corroded Metals/Equipment
Scale Formation Skin and Eye Irritation
Shorter Filter Runs Etched or Stained Plaster
Skin and Eye Irritations Destruction of Total Alkalinity

What Happens if TA (Total Alkalinity) is not right?

High Total Alkalinity Low Total Alkalinity
Hard to Change pH Rapid Changes In pH
Scale Formation Corroded Metals/Equipment
Cloudy Water Skin and Eye Irritation
Skin and Eye Irritation  
Poor Sanitizer Efficiency


Does the Hardness of my Water matter?

Sometimes referred to as “total hardness”, calcium hardness is a measurement of minerals in your water including calcium and magnesium. You do want your water to have some level of hardness. If the water does not have enough calcium, the water will draw from other minerals, including copper, aluminum and iron, (e.g., heating elements, pump seals, and internal parts on gas fired heaters). This will result in equipment corrosion. If there is too much hardness, you will see scale formation on the spa’s interior and the water will take on a cloudy appearance. Because of this, it is recommended that you fill your spa with water from a softener instead of tap water.

So what should the calcium reading be? Between 100- 250 PPM’s for acrylic finish, and 250-450 PPM’s for plaster finish. Let’s look at some potential problems if it goes unchecked.

Hardness too Low Hardness too High
Deterioration of Metal Components in Spa Equipment Scale Formation On Surfaces
Unwanted foam Cloudy water


What is Shock and How do I Shock My Hot Tub?

Shock is an oxidizer that is used to destroy organic contaminants that have been able to escape normal daily sanitation. Oxidation involves the transfer of electrons, and when hot tub water contaminants or pathogens are oxidized, they lose electrons, and quickly expire, or cease to exist.

Hot tub shocks are made from a powdered form of oxidizer, either a form of granular chlorine, non-chlorine potassium sulfate salts or liquid chlorine (bleach). When using a biguanide sanitizer system (Aqua Silk), the spa shock is made of liquid hydrogen peroxide, which can not be used in a bromine or chlorine treated spa/hot tub.

There are 3 main reasons to shock a spa:

  1. To destroy excessive contaminants in a hot tub after use by several people,
  2. To reactivate bromide ions into active bromine
  3. To kill algae, bacteria, viruses and pathogens that may escape your normal daily sanitation chemical.

When should you Shock a Hot Tub?

Maintain the chlorine level in the hot tub by adding shock to the tub once a week during the warmer months, or every two weeks during winter if the hot tub doesn’t get used as much as it does in the summer. Shock is added to the water during the evening so it has at least 12 hours to work in the water. Sunlight causes shock to dissipate quickly.

How to Shock a Hot Tub?

Step 1 – Check the pH level

Before you shock your hot tub, you need to check the pH level of the water.

Although you might have little or no knowledge of science and chemistry, it’s actually very easy to do a pH test of your water.

With the pH reading at the correct level, you’re ready to shock your hot tub.

Which Shock Do You Need?

First off, the shock you use depends on the sanitizer you use. As we mentioned before, there are three main sanitizers used in hot tubs:

  • chlorine
  • bromine
  • minerals


If you use chlorine tablets or chlorine granules in your hot tub, you need to use chlorine granules to shock your water.

These destroy any contaminants and matter in the water powerfully and quickly. They also turn the old dead chlorine sanitizer into a gas, which then escapes into the air.

The negative side of using chlorine granules to shock your hot tub is that they give off a strong chlorine smell while they’re doing their work. This is unpleasant, and might even irritate your eyes and nose. The answer is to shock your hot tub overnight, to reduce the effect.

To shock your portable hot tub with chlorine granules:

  • Fill a bucket with water from your inflatable hot tub.
  • Dissolve 1 oz of granules for each 500 gallons of water your hot tub holds in the bucket (that’s about 1 tablespoon of granules)
  • NEVER add water to chemicals – always add your chemicals to water!
  • Turn on the air bubble jets and add the dissolved chlorine
  • Keep the cover off and leave the air bubble jets going for an hour, then switch them off.
  • Leave your hot tub cover for a further 15-20 minutes, to let the gases escape.
  • Put the cover back on and leave your hot tub overnight (or for several hours if you’re doing it during the day time).
  • Test the chlorine level of the water, to make sure it’s in the acceptable range of 1-3 parts per million (ppm). If not, test every 30 minutes or so until the level is correct.
  • Your hot tub is now safe and ready to use.

how to shock your inflatable hot tub chemical granulesIf you already use chlorine granules to sanitize your hot tub, then you don’t need to buy a special chlorine shock. You can use the same chlorine granules you use as your sanitizer.

If you use chlorine tablets, however, you are going to need to buy a container of chlorine granules


If you use bromine as your water sanitizer, than you need to use bromine granules to shock your hot tub.

Although bromine isn’t as popular among hot tub owners as a sanitizer, it does have one advantage over chlorine when used as a shock: it doesn’t give off that strong chlorine smell.

The procedure for shocking your hot tub with bromine granules is the same as for chlorine granules:

  • Fill a bucket with water from your hot tub and add 1oz of bromine granules for each 500 gallons of water your hot tub holds (that’s about 1 tablespoon of granules).
  • Stir the granules until they are dissolved.
  • Turn on the air bubble jets and add the dissolved bromine
  • Keep the cover off and leave the air bubble jets going for an hour, then switch them off.
  • Leave your cover off for a further 15-20 minutes, to let any gases escape.
  • Put the cover back on and leave your hot tub overnight (or for an hour if you’re shocking your hot tub in the day time).
  • Use a test strip to check the bromine level of the water. It needs to have a reading between 2-6 parts per million (ppm). If it’s too high, re-test every 30 minutes.
  • When the bromine level is within the correct range, you can start using your hot tub again.

If you use bromine granules in your hot tub already, then you can also use them as your shock. If you use bromine tablets in your chemical float, however, you’ll need to buy some bromine granules.


Strictly speaking, a mineral sanitizer isn’t a sanitizer! It’s a mix of silver, copper, and other minerals. However these only act to reduce the amount of chlorine or bromine you use as a sanitizer. So if you choose a mineral sanitizer, you still need to add either chlorine or bromine to the water.

What this means, is that if you use chlorine along with your mineral sanitizer, then you need to use chlorine granules as your shock. If you use bromine along with your mineral sanitizer, then you need to use bromine granules as your shock.

Using Non-Chlorine Shock In Your Hot Tub

If you visit hot tub blogs or read what people are saying , you might see discussion around using a non-chlorine shock. A good example of this is a product like Oxy-Spa Non-Chlorine Hot Tub Shock.

This gets mixed reviews from hot tub owners, with some saying it’s the best thing ever, while others say it doesn’t work at all, that it turns their water slimy and even yellow!

In our experience, it is a good alternative to chlorine and bromine, and it’s useful if you have sensitive skin that reacts to chemicals. However, you need to keep a constant eye on your pH levels, your sanitizer levels, and also shock your hot tub at least once a week.

So although its big advantage is the lack of chlorine or bromine in your hot tub water, you’ll need to work harder if you choose to use one of these non-chlorine shocks.

Hope you have enjoyed the article! Happy Hottubing!