A hot tub needs the right chemicals to be safe and clean. Chlorine and bromine are the most common sanitizers. Both are available in tablets and granules. Both are harsh on skin and can irritate eyes, cause brittle hair, and emit unpleasant odours at too-high levels.
Never mix pool and Hot Tub Chemicals. This can be harmful and costly.
Chlorine
Chlorine is a greenish-yellow, diatomic gas with a sharp scent. It is water soluble and reacts quickly with organic compounds (such as suntan lotion, oil or moisturizers left behind by bathers) to produce chlorine dioxide which attacks bacteria and disinfects your hot tub.
Chlorine also oxidizes proteins and other materials in the water to form hypochlorous acid, which penetrates cells and damages their structure. At high concentrations, chloride ions can disrupt the respiratory and circulatory systems, burn the skin and cause gastrointestinal tract irritation.
The most common route of exposure to chlorine is inhalation. At low levels, this causes irritation to the eyes and skin. At higher levels, it can lead to bronchospasm and noncardiogenic pulmonary edema. The odor of chlorine is strong enough to provide early warning, but prolonged exposure can cause olfactory fatigue or adaptation, reducing your awareness of the presence of the chemical in air.
You can add chlorine to your hot tub by adding granules or tablets. Read the instructions on your sanitizer container carefully, and follow the recommended dosage for your hot tub size. To avoid overdosing, measure the sanitizer and add it slowly to the water. For best results, test the water often and make adjustments as needed.
When using granules, mix the sanitizer with water until it is dissolved. Pour the solution into your skimmer basket or into a chemical feeder. For chlorine or bromine tablets, follow the manufacturer’s instructions for use, and place two tablets into a chemical floater or directly into your hot tub skimmer.
Regardless of the sanitizer you choose, your hot tub will require frequent water replacement. As it combines with contaminants in the water, chlorine produces waste products called chloramines that reduce its effectiveness. To re-establish the proper balance, you must shock your hot tub on a regular basis. This is one of the reasons that many people choose to switch from chlorine to bromine, as it requires less water replacement and does not produce chloramines. However, it is still necessary to test the water regularly and do a thorough deep clean on a monthly basis.
Bromine
When thinking about sanitizers for your hot tub, chlorine and bromine are probably the first two chemicals that come to mind. Both kill contaminants like bacteria, algae and soap residue, but they do it in different ways. Chlorine is a strong oxidizer, which means it invades and destroys contaminants from the inside out. As it works, however, it also creates waste products called chloramines — these are responsible for the stinging, drying and stinky reputation chlorine gets.
On the other hand, bromine is a weak oxidizer. It is less apt to produce chloramines, but it is also not as effective at attacking contaminants directly. It is more stable in warm water and tends to help balance your spa’s water chemistry more effectively than chlorine.
It is available in tablets, granules, and liquid form. In the case of tablets and granules, the amount you add to your hot tub is proportional to the volume of water it contains. Add these according to the manufacturer’s instructions, then test your water to make sure you have the right levels of sanitizer.
Bromine is also available in a “pool sticks” or dispenser that can be filled with liquid or powdered product, then placed in your hot tub. Some of these dispensers also act as a timer, so you know exactly when to replace the product. This type of sanitizer requires more attention and finagling than a tablet or granules.
In addition to sanitizing, bromine is also used as a disinfectant and deodorizer. Some compounds containing bromine are also used as sedatives and in fire retardants.
Although it is less toxic than chlorine, exposure to bromine should be avoided. It is a respiratory irritant, especially at higher concentrations. The severity of symptoms depends on the amount, route and duration of exposure. It is also a skin and eye irritant. When released into the air, bromine forms a gas that is heavier than air and will settle in low areas. The vapor can burn lungs and penetrate the skin. This is why it is recommended that you wear a face mask and protective eyewear when using these products.
pH Adjusters
A hot tub can make you feel good about yourself by relaxing tense muscles and reducing stress, but the water must be in balance to ensure it remains healthy. Hot tub chemicals include pH increasers and decreasers, metal removers (if using rainwater or bore water) and sanitizers such as bromine and dichlor to keep the water safe. The water should be tested regularly to check the levels of chlorine, free bromine and total alkalinity, which should be between 7.2 and 7.6 ppm.
Most people are familiar with the concept of acids and bases from high school chemistry class. The pH scale measures how acidic or basic the water is with seven being perfectly neutral. If the water is too low (acidic) scale will build on the wetted surfaces of the hot tub, and if it’s too high (basic) the metals within the wetted surfaces can corrode.
Using a spa water test kit is the best way to monitor the pH level of your spa, and if it’s outside the recommended range you can use a pH increaser or decreaser to get it back into balance. When introducing these products to the water it’s important to follow the instructions in the owner’s manual carefully, as too much can have an adverse effect on other aspects of your hot tub water, such as the total hardness and calcium level.
Some pH adjusters, like sodium bicarbonate (baking soda) will also raise the total alkalinity level of your hot tub, which is important if your TA is too low. Alternatively, there are products that focus solely on raising the TA such as a buffered TA increaser that also contains three electrolytes to help maintain osmotic balance.
Muriatic acid is an alternative to increase or decrease both the pH and TA, but it is extremely caustic and requires the use of safety glasses, chemical-resistant gloves and a lot of caution. The safer alternatives to this are products such as the non-caustic BlueGOLD pH solutions which are also less expensive. These are available as granular or liquid and are not harmful to plants or natural cloth fibers, and they are also safer for the environment because they don’t generate heat upon neutralization.
Alkalinity Adjusters
In addition to chlorine and bromine, balancing total alkalinity (TA) levels is essential for keeping your hot tub water clean and healthy. TA balance keeps your pH level between 7.4 and 7.8 which allows your sanitiser to work at its best.
When a hot tub’s TA level is below 80 ppm, the water can become corrosive and acidic which can damage your equipment and cause eye irritation and skin sensitivity. When a hot tub’s TA levels are above 120 ppm, the water can become cloudy and allow scale to build up on your equipment and surfaces.
Both low TA and high TA can be caused by bathers’ body oils, sweat, lotions, detergents or other chemicals in the water as well as hard water from bore or rain water sources. The chemistry of hot tub water is different from pool water due to the mineral content which can create issues with pH and TA levels.
If your TA is below 80 ppm, use an Alkalinity Increaser which is often called baking soda to bring it back up to the desirable range. If your TA is above 120 ppm, you need to use a pH Reducer which is also known as sodium bisulfate.
While most hot tub owners find balancing their water easy, there are some who have difficulty getting their pH and TA into the desired range. The reason for this is that there are many different water conditions across the country and even within a city or town which can influence the chemistry of your hot tub water.
Whether your hot tub’s water is from a municipal source, well or a private bore system, it will need to be treated before adding any chemicals. The first step is to remove any metals present which can interfere with the stability of your sanitiser levels and turn your water an unattractive color. This can be accomplished by using a metal remover before you add any other chemicals. The next step is to balance the pH and TA levels which you can do with a test strip or liquid pool chemical tester kit.