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What chemicals should I put in my hot tub for the first time? | HotSpring Spas

What chemicals should I put in my hot tub for the first time?

Hot tubs are an amazing source of relaxation and leisure for people throughout the world. Whether you are using your brand new tub to relax tense muscles or just to simply destress from the day, you will want to make sure you are putting the right chemicals in the very first time you use it to ensure safety for you and your family. 

The chemicals you will need to start your hot tub include a pH increaser, pH decreaser, calcium hardness, a metal removal (if using water from rainwater tanks or bore) and a sanitiser. The chemicals have to go in a certain order for the process to work. Your final goal should be to balance your pH level between 7.4 and 7.6 and your alkalinity between 100-200 parts per million.

If you just bought a brand new hot tub, chances are you are really excited about your new purchase and want to do everything you can to make it a safe and fun experience for you, your family and your guests. Keep reading to learn the exact chemicals, methods and tips for starting your hot tub for the first time. 

While the chemicals you’ll need to add to your spa will depend on your situation, a basic list of chemicals every spa owner should have includes:

  • Spa sanitiser such as bromine or chlorine.
  • A pH increaser and decreaser such as FreshWater® pH/Alkalinity Up and FreshWater® pH/Alkalinity Down
  • Spa shock solution, such as chlorine or MPS.

Can I use my hot tub without any chemicals?

First things first: do you even need chemicals? What happens if you use a spa pool without chemicals? 

Initially not much will happen at all. If you fill your spa and heat the water you’ll enjoy a lovely introductory soak.



The issues will begin slowly, rearing their head after a day or two, before becoming exponentially worse as time goes on. It will start with a slight odour and an accumulation of bubbles when you use the jets. The water soon becomes cloudy and discoloured, and the smell intensifies. Soon you begin to spot algae and mould in your spa, as bacteria, fungus and other intruders take your machine over.

A spa pool is not like a spa bath – you don’t drain it after every use. You need your water to last, and if you want the finest soaking experience possible, you want that water to be clean, clear, soft and fresh. Hot tub chemicals are built to deliver exactly that.


Cleaning the Hot Tub Before Starting It

It is also important to properly clean all areas of the hot tub that are exposed to water before you start pouring chemicals in there for the first time. Use a soft cloth and non-abrasive cleaner to wipe down the shell and cover of the hot tub. Make sure to rinse thoroughly to reduce foaming. 

Spa Metal Removal:

Metals are often present if you’re using bore or rain water to fill your hot tub. When starting your hot tub for the first time, it is a good idea to use a metal remover to neutralise your water before putting in any further chemicals. The best system to use is the Fresh Start® Clean Screen filter that attaches to your hose as you fill your hot tub with water. Note that this step is not required if you are using water supplied by the council. 

Calcium Hardness:

Calcium Hardness is the total amount of magnesium and calcium dissolved inside the water of your hot tub. Measuring the calcium hardness lets you know how much calcium is present in your water. Taking this step is important because low levels of calcium hardness can lead to damage and erosion of your hot tub. Therefore, you will want to add calcium hardness when starting your hot tub to make it level at the recommended range. The recommended range of calcium hardness for a hot tub is around 15-400 parts per million.  

Chemicals To Put In When Starting Your New Hot Tub 

Before putting in any kind of chemicals, the first step is to fill your hot tub with water. After filling your tub, you can check for chemical levels. Different hot tubs come in different sizes and brands. The amount of chemicals you will use for the start-up process will vary depending on the size and brand of the tub. You need to know how many gallons of water your hot tub will hold. You can usually find this information in the user manual that comes with the hot tub. The owner manual also has recommendations for how much water to use with the specific chemicals needed to start a hot tub.  

After filling your hot tub with water, you will want to adjust your pH level and complete alkalinity. You can purchase tester strips to help you balance the pH level and alkalinity. You simply add the pH increaser or pH decreaser as needed until the tester strip shows the pH level to be between 7.4 and 7.6. Similarly, the alkalinity should be between 100-120 parts per million.  

You must balance your pH level before moving onto the next step of the process which is adding a sanitiser to the water. If your pH level is not balanced, the sanitiser might not be effective. When you are adding chemicals to the water, you will want to turn on all of the therapy pumps and spread the chemicals evenly throughout the water. 


Are swimming pool and hot tub chemicals the same?

“What chemicals do I need for a hot tub?” you might ask? The answer is not swimming pool chemicals. This is a common misconception and can be a costly one. 

It’s important to note that swimming pool chemicals and hot tub chemicals are very different, and are not interchangeable. They are really designed for two very different jobs: one where a large pool of water sits at relatively stagnant and at a relatively low temperature, and one where water is enclosed, heated and pumped through high pressure jets.

If you use swimming pool chemicals in your spa pool, you risk doing real and costly damage to the machine, and the opposite is also true. Always purchase spa pool-specific chemicals to ensure your spa lasts the distance, and your soaking experience is as good as it can be.

Sanitising the Hot Tub

After your hot tub has reached the recommended pH and alkalinity levels, the next step is to sanitise the hot tub and the water. There are many different types of sanitisers. The main forms of sanitisers are chlorine, bromine, minerals and salt systems. Each type of sanitiser comes with its own advantages and disadvantages.  


Chlorine is the most commonly used sanitiser because it offers several advantages over the others. Chlorine is more cost-effective than non-chlorine sanitisers. It is also easily manageable making it a convenient option. Chlorine is also a very aggressive algae and bacteria killer so it gets the job done well. It can be compared to how effective bleach might be at killing bacteria in your bathroom. The downfall of chlorine is the strong scent that comes with it. A common misunderstanding around chlorine is that the smell results from the actual chlorine itself. The smell comes from waste products called chloramines. Chloramines are formed during the oxidising process that happens when chlorine kilts contaminants by breaking down the chemical components. If you can smell the strong scent that chloramines give off, chances are you need to add more chlorine in your water because it got used in the oxidizing process. 


The use of bromine in an automated sanitation system is banned in certain countries as well as some states in the USA. Bromine salt systems require up to a staggering five times more chemicals to operate than our FreshWater™ Salt System. These chemicals are harsh on the skin, emit a strong odour and lead to users requiring a shower following their spa. Contaminants end up staying in the water for a longer period of time before being destroyed so you will have to wait longer to accurately test your water levels. You should also be very careful not to use too much bromine when sanitising your tub because bromine can build up over time. Bromine also burns off way quicker under the hot sun because it is unstabilised. Therefore, choosing a chlorine sanitiser for an outside tub might be more effective. 


Mineral sanitisers use either a bactericide (silver) or algaecide (copper) to sanitise the hot tub. Using a mineral-based sanitiser allows you to use less chlorine so the water will be more gentle on your skin. However, minerals can not successfully sanitise the hot tub by themselves. You will need to add at least some chlorine if you want to properly sanitise your hot tub. Minerals are not that expensive but if you take into account that you will also need to purchase chlorine, the final cost could still be high. You can still eliminate the negative scent that chloramines produce when you use minerals because you will be using very little chlorine. Also, minerals can be easily managed. They come in a pre-packaged dosing stick. All you have to do is add the stick to your filter and replace it every three or four months. 

Getting a brand new hot tub is a very exciting moment for most customers. The best way to ensure safety for yourself, your guests, and the hot tub is to use a pH increaser, pH decreaser, metal removal (if using bore water), calcium hardness and a form of sanitiser when starting your hot tub for the first time. 


Q: How much chlorine do I add to the hot tub the first time?

A: When you fill or refill your spa pool, it needs to be treated with a relatively high dose of sanitiser. You should aim to add 40g of chlorine granules per 1000L of water in the beginning, and let the level drop to 3-5 milligrams per litre before using the hot tub. 

Q: What is the most commonly used sanitiser when starting a brand new hot tub?

A: Chlorine is the most commonly used sanitiser due to the several advantages it offers over the others. Although it comes with an odour, it is the most effective way to sanitise your hot tub.

Q: Is there a way to get around putting chemicals in the hot tub?

A: The only way to get around it is you drain the water and refill it after each use. You will also want to make sure that the water is never in the hot tub for longer than 12 hours. If you want to keep the same water for multiple uses, you should balance the hot tub using the chemicals mentioned above. 

Q: How long should you wait to get in after putting chemicals in the hot tub?

A: You should wait about thirty minutes. You need to let the chemicals completely dissolve into the water.

Q: Where can I purchase hot tub chemicals suggested in this article?

A: We recommend you purchase your hot tub chemicals from a reputable hot tub supplier that stocks high quality products that do not contain fillers or bulking agents. We recommend Spa Pools Online or your local Hot Spring dealer.


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