hot tub chlorine

Hot tub chlorine FAQ: Total vs free chlorine

Alkalinity, pH, calcium hardness. When you are testing your hot tub water, there’s a few chemical levels to consider. But you might be curious why the test strips have two different chlorine levels — total chlorine and free chlorine. 

Isn’t chlorine just chlorine? 

Chlorine is added to your hot tub water to help keep it clean and kill germs, bacteria, algae, and other contaminants. 

When you add chlorine to your water, you only have one bottle in your tool kit. However, there is more than one type in your hot tub water. It’s important to know the difference between the chlorine levels and what each is so that you can keep it as clean as possible.

hot tub chlorine
Chlorine is an ideal sanitizer for hot tubs. Not only is it affordable, it’s easy to use. Master Spas’ EcoPur mineral filtration system utilizes chlorinating granules to keep your water clean and clear.

Hot tub chlorine 101

Chlorine is a popular sanitizer for hot tubs. Not only is it affordable, chlorine is easy to add to your water.

How does it work?

When chlorine is added to your water, there’s a reaction called oxidation. Algae, bacteria, and other elements can’t grow when there’s enough sanitizer in the water.

The amount of chlorine you add to the water will depend on a variety of factors. The size of your hot tub, how often you use the hot tub, and how many people use the hot tub will affect the amount of chlorine needed. 

In addition, anything that you have on your body will affect chlorine levels. For example, if you have lotion on, the chlorine will have to work harder to break that down. Your chlorine level will drop and you will need to add more.

An important thing to remember is that if other chemicals in your hot tub are not balanced, your chlorine can’t work. The general rule of thumb is to first adjust alkalinity and then pH. Once these values are within range, you can add chlorine.

How often do you add chlorine? Unless you are using your spa every day, you probably won’t need to add it more than two to three times per week.

testing hot tub water
When you test your hot tub water, you will want to make sure that the free chlorine levels are higher than the total chlorine.

Types of chlorine in hot tub water

Test strips are easy to use and a popular way to measure the chemicals in your spa. You can also use a liquid test kit to check your water.

No matter how you choose to check your water, you should know what the different values mean.

Free chlorine

What does it mean if your chlorine is free? Before you get too excited, we’ll let you in on this secret. “Free” has nothing to do with the price.

Free chlorine is the chlorine that’s  “available” to keep your hot tub water clean.

As a hot tub owner, you will add sodium dichlor granules to your water. These granules dissolve in the water and then get to work, attacking the things you don’t want in your water.  

Once the chlorine attacks bacteria and other contaminants, it’s no longer “free” and this chlorine level will drop.

Your free chlorine levels should be between 1 and 3 ppm. 

Combined chlorine

What happens to the free chlorine once it kills contaminants? Does it just disappear?

Yes and no.

The free chlorine attaches itself to the contaminants, forming chloramines. These compounds, also known as combined chlorine, are a part of your total chlorine. However, combined chlorine can’t keep your water sanitized. 

And while more can sometimes be better, you don’t want a high level of combined chlorine in your water. 

When you have a high level of combined chlorine, your hot tub water might smell like chemicals

Total chlorine

Total chlorine is just what it sounds like — it’s the total amount of chlorine in your hot tub water. When you are testing your water for total chlorine, you are measuring the sum of free chlorine and combined chlorine. 

Ideally, you want free chlorine to be equal to total. If free begins to test lower than total, it is a sign that some of the chlorine is bound up and “combined.”

Is your combined chlorine too high? You will need to shock your hot tub water. Shocking your hot tub water helps “free up” the combined chlorine and help increase the free chlorine levels.

chlorine bromine hot tub
The EcoPur Charge system requires less chemicals than other systems, making it gentler on skin. You will need less chlorine to keep the water clean. If you use bromine, it can stick to your swim suit and skin.

How to buy a hot tub

Are you ready to turn your backyard into an oasis? A Master Spas hot tub can help you relax and unwind in the convenience of your backyard. You can click here to discover our secrets to creating a backyard oasis. Or, contact your local Master Spas retailer to learn more about swim spa ownership. Wondering how much a hot tub costs? You can request a quote here.