Every hot tub owner knows that they need to add chemicals to their how tub water but few actually know what all of these chemicals do. Today, we will explain what all these chemicals do, and give you tips to help you get the most out of your chemicals.

What Do Hot Tub Chemicals Do?

Hot tub chemicals generally perform one of three roles:

  1. Killing bacteria.
  2. “Balancing” the water.
  3. Improving the quality of your bathing experience.

Sanitizing Chemicals

Sanitizing chemicals are used designed to kill bacteria; keeping the water clear and safe to use. Simply put, without sanitizing chemicals (either bromine or chlorine), bacteria in the hot tub water would quickly begin to multiply and cause issues with water clarity and safety.

Sanitizing chemicals come in to main forms; tablets and powder. While both are designed to do the same job they are actually used quite differently.

Tablets are designed to dissolve slowly over the course of several days while powdered sanitizers are designed to dissolve instantly.

Since powered sanitizers dissolve so quickly, they have to be added regularly; typically after every use or every 2-3 days when the hot tub is not in use. Tablets, on the other hand, only need to be added around once per week.

Powdered sanitizer can also be used to “shock” the hot tub’s water. “Shocking” is the process of burning off dead bacteria and spent sanitizers that are no longer able to do their job. Removing these particles from the water allows your sanitizers to do their jobs more efficiently. If you didn’t regularly shock your hot tub, these particles would build up in the water and you would need to use more and more sanitizer to keep the water clear and safe to use.

Balancing Chemicals

Water balance is the relationship between different chemical measurements in your pool, swim spa or hot tub water. It is based around how water reacts with other particles. Essentially, water dissolves and holds minerals until it becomes saturated and cannot hold any more. We will refer to this as the water’s “saturation point”. The goal of water testing is to get your water as close to the saturation point as possible.

When the water balance dips below the saturation point, it becomes corrosive. Water that is corrosive will try to saturate itself by dissolving everything it comes in contact with.

When water is above the saturation point, it becomes scale forming. It can no longer hold all of the minerals that are dissolved in it. The excess minerals will then “fall out of solution”, grouping together and forming scale on any surfaces within the water.

Water balancing chemicals are designed to do one of 4 things:

  • Increase Alkalinity.
  • Increase pH.
  • Decrease pH and/or Alkalinity.
  • Increase Calcium Hardness.

Water Improvement Chemicals

Although they all perform very different functions, water improvement chemicals are all designed to improve your bathing experience in some way. These chemicals are optional and are added based on your own personal preference. Common water improvement chemicals include:

  • Clarifiers. These are designed to help your filters work more efficiently to either quickly clear cloudy water or give clear water a sparkling appearance.
  • Biofilm Removing Chemicals. These chemicals break up biofilm that builds up in the plumbing of your hot tub. Removing biofilm helps your sanitizer to work more effectively and reduces water quality issues such as foamy or cloudy water.
  • Anti-Foam. These chemicals lower the surface tension of the water to prevent bubbles from stacking up on one another to create foam.
  • Stain & Scale Prevention. These chemicals coat minerals and metals like calcium and iron that are commonly found in water. By coating these particles, stain and scale prevention chemicals stop them from clumping together to form scale and stains on the surfaces of the hot tub.
  • Aromatherapy Oils / Crystals. Aromatherapy chemicals are designed simply to give the water a more pleasant scent. Commonly either oils or quick dissolving crystals, these chemicals typically dissipate after a couple of days and will need to be reapplied.

How Often Should You Add Chemicals To A Hot Tub?

Sanitizing chemicals should be added as often as you need to in order to maintain an acceptable residual of your sanitizer in the water. If you use tablets this generally means adding 3-4 tablets to your tablet dispenser once per week (although this varies based on how big the hot tub is and how much it gets used). If you use powdered sanitizer, adding a little bit to the water after each use is generally the best approach.

Along with maintaining a good level of sanitizer in the water, you will also want to shock the water once per week to keep the sanitizer working at peak efficiency.

Note: No matter whether you use powdered sanitizer or tablets you should test the water before every use to ensure that your sanitizer level is in the acceptable range. If your sanitizer level is consistently out of range you should adjust the amount of sanitizer you add to the water on a regular basis.

How To Properly Add Chemicals To A Hot Tub

Believe it or not, how you add chemicals to your hot tub water can make a big difference in how effectively they do their job. To ensure the chemicals you add to your hot tub water are working at peak efficiency you will need to:

  1. Make sure the jets are turned on. Turning the jets on keeps the chemicals suspended in the water as they dissolve and prevents them clumping together on the seats or floor of the hot tub. This ensures that the chemical dissolves fully and is spread evenly throughout the water.
  2. Add each chemical at least 15 minutes apart. Spacing out your chemicals by at least 15 minutes give each chemical the opportunity to fully incorporate into the water before the next chemical is added. This prevents the chemicals interacting with each other in ways that can reduce their effectiveness and negatively affect the water balance of your hot tub water.

An exception to these rules is when you add sanitizing tablets to your tablet dispenser. These dissolve so slowly that they will not affect any other chemicals being added to the water.

Some chemicals (most commonly enzyme based chemicals) are also negatively affected by high levels of sanitizer. For best results, these should be added at least a couple of days after you shock your hot tub as shocking leads to temporarily high levels of sanitizer that can severely restrict the effectiveness of these chemicals.

Note: When shocking your hot tub you will also want to ensure that you leave your hot tub cover fully open for at least 30 minutes after adding your shock treatment. This is because part of the process of shocking relies on gases such as nitrogen being released from the water. If you close your cover after shocking these gases aren’t able to escape; reducing the effectiveness of the shock treatment and potentially damaging the underside of your hot tub cover.

Read More: Can You Run A Hot Tub Without Chemicals?

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