Is Hot Tub Shock and Chlorine the Same Thing?

Owning a hot tub can feel a lot like you’ve enrolled in an unwanted chemistry degree. Seeing as both of these much-used products have chlorine as a base ingredient, are they not just the same thing?

Although both chlorine sanitizer and chlorine shock contain the same active chemical, they have vastly different concentrations. Chlorine sanitizer is used to sanitize contaminants and shock is used to oxidize the water, which enables the sanitizer to work at maximum capacity. Non-chlorine shock is a chlorine-free oxidizer.

This article is going to show you:

  • What makes chlorine and shock different
  • Whether the two products are interchangeable
  • How and when they should be used

Chlorine vs shock

Chlorine acts as a sanitizer for your hot tub water. Sanitizers are used to destroy bacteria and other disease-causing germs, leading to a clear, clean, and healthy spa. 

There are three types of chlorine found in hot tubs. Free available chlorine (FAC) is the purest state of chlorine. This type of chlorine is unused and available to sanitize your spa water.

Combined chlorine is chlorine that is used up and has lost its sanitizing power after attacking the contaminants in the water. The last one is total chlorine, which is the sum of free chlorine and combined chlorine levels. 

Furthermore, there are two categories of chlorine: stabilized and unstabilized chlorine. Unstabilized chlorine is the purest form of chlorine, while stabilized chlorine contains cyanic acid (CYA), which is used to protect chlorine from UV light. Unstabilized chlorine is mostly used in swimming pools and should never be used in hot tubs.

Chlorine comes in 3 forms: granules, liquid, and tablets. Sanitizing granules contain stabilized chlorine to protect from sunlight, which makes them ideal for outdoor spas. Granules contain around 56% available chlorine.

Chlorine tablets also contain stabilizers, making them perfect for outdoor hot tubs that are constantly exposed to the sun. They contain 90% available chlorine and dissolve slowly over the course of several days inside a chlorine dispenser.

On the other hand, liquid chlorine lacks a stabilizer and contains 12% available chlorine. In addition, it dissolves fast, making it perfect for raising chlorine levels quickly. In terms of amount, two 3-inch chlorine tablets equal one gallon of liquid chlorine.

Shocks act as an oxidizer for the water in your hot tub. They are also used to reduce combined chlorine and increase free chlorine. 

The purpose of an oxidizer is to break down organic matter, bacteria, and other contaminants in the water. This breaking down process is carried out by removing the electrons found in the pollutants.

The difference between chlorine and shock is that shock has a higher chemical strength than chlorine. Chlorine is constantly working to kill pollutants. This causes it to lose its effectiveness, leading to the formation of more combined chlorine.

You’ll need to use a shocking chemical to destroy the combined chlorine and raise the FAC level. Therefore, to thoroughly sanitize your hot tub water, you’ll need both a sanitizer (chlorine) and an oxidizer (shock).

Chlorine shock vs non-chlorine shock

There are two types of shocks: chlorine and non-chlorine shock. They are both available in powder, granulated, and liquid forms. 

Chlorine shock has a high pH and dissolves quickly. Non-chlorine shock also dissolves quickly but has a low pH. Additionally, it is less effective than chlorinated shock and, as such, cannot kill off bacteria and algae.

The upside to using non-chlorine shock is that you can use your hot tub 20 minutes after applying it. Furthermore, non-chlorine shock works well under the sun or extreme heat and leaves no chlorine odor in your spa.

Can I use chlorine as a shock treatment?

No, you can’t use chlorine as a shock treatment because it is not as concentrated and powerful as a shocking chemical. Sanitizers and oxidizers have different functions. It is crucial you know these functions as well as the differences between the two chemicals.

Can I use shock instead of chlorine?

No, you can’t use shock instead of chlorine because shock is too concentrated. The purpose of a shock is to kill new pollutants that enter the hot tub. This function can only be carried out after a chlorine sanitizer has been added to the spa and loses its sanitizing power.

How and when to use chlorine sanitizer

You should use chlorine sanitizer in your hot tub at least once a week. Some people prefer to use a small amount in the spa after each use. However, the number of times you add chlorine to your hot tub depends on how often the spa is used.

A hot tub used once a week for 15 minutes should be sanitized every 2-3 days, while a hot tub used more frequently may require a chlorine top-up every day.

Another factor that determines how often you should add chlorine is the total number of bathers in your hot tub at a time. 

If many people use the spa, it will become dirtier faster. This will require the hot tub to be sanitized more frequently since the chlorine in the tub loses its effectiveness with each person added.

Additionally, never add shock and chlorine at the same time. Shock the water first. Then once the chlorine levels drop below 5 parts per million, you can add more chlorine.

Essentially, you need to measure the amount of chlorine in your hot tub daily. You can do this by using a test strip. The test will help determine how often you should add more chlorine to the spa.

How and when to use chlorinated shock

You should use chlorinated shock at least once a week during warmer months. For colder months, you should shock your hot tub once every two weeks since spas are generally used less frequently during this period. 

It is recommended you add chlorine shock after filling the tub with fresh water or after heavy use of the spa. 

It is also recommended to add the shock in the evening, giving it at least 12 hours to work in the water. Another reason you should add the chlorinated shock in the evening is that sunlight causes it to dissipate quickly.

Remember that shocking your hot tub water increases chlorine levels and can lead to chemical damage. Therefore, do not shock your spa after every use.

Joshua Milton

Joshua Milton is a seasoned hot tub enthusiast. With many years of experience in the industry, he offers valuable insights on hot tub maintenance, health benefits, and relaxation techniques.

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