How Much Chlorine To Add To Hot Tub First Time?

How Much Chlorine To Add To Hot Tub First Time?Chlorine is one of the most effective water sanitising agents we use when humans and water meet. Your hot tub is no exception. But a common question for a newbie hot tubber is “how much chlorine to add to hot tub first time?”. totallyhottubs are here to answer this for you.

Here are all the useful facts about chlorine and hot tubs and how to make sure you’re always having a safe and healthy (as well as fun and relaxing) ‘tubbing experience.

How Does Chlorine Work In A Hot Tub?

Chlorine is highly effective at killing bacteria and pathogens found in water. That’s why you’ll find it in use in swimming pools and other places where humans want safe, clean water.

This is important.

Because hot tubs might be full of balmy water that is simply delicious to duck into for a fun and pleasurable evening (or morning or afternoon!). But, over time, all kinds of organic debris – think hair and dead skin – as well as lotions, oils, and so on can start to build up.

So if you want to keep your tub clean and safe, there are two different options when it comes to cleansing chemicals. Chlorine is broadly agreed to be the better choice of the two.

The kind of chlorine granules and tablets used for hot tub and spa cleanliness are usually made from a mixture of sodium chloride, sodium hydroxide, and hydrogen. When you dissolve this in water, it creates a kind of acid that dissolves anything that could be dangerous.

However, that acid becomes less active over time, meaning you need to regularly top up your hot tub’s chlorine levels.

How Much Chlorine To Add To A Hot Tub The First Time

On average, a good rule of thumb is to add roughly one-and-a-half times as much chlorine the first time you use your hot tub as you do for routine top-ups. This is necessary because the chlorine needs to pass through your tub’s filtration system.

A good approximate measurement for a starting chlorination level is one teaspoon of chlorine granules per 100 gallons of water in your tub. Your general goal is:

  • Roughly 5 to 8 parts per million of chlorine as an initial dose
  • Allow this to tail off to an average of between 2 and 4 ppm afterwards
  • Aim for between 1.5 and 3 ppm before you actually get into your tub

Overall, the best approach for chlorine isn’t to go by amount. What you’re really looking for is a good balance between the acid that the chlorine produces and the chemical balance in your tub.

To discover this, it’s a good idea to get some hot tub test strips.

These are cheap and readily available. A good pH level for your tub (balancing acidity with alkalinity) is between 7.4 and 7.6, with an alkalinity between 100 and 200 parts per million.

How To Tell If There Is Too Much Chlorine In Your Hot Tub

The most sensible way to check if there is too much chlorine in your hot tub is to test it using those pH or chlorine test strips. Compare this with manufacturer guidelines and the numbers mentioned above.

Some common physical signs that there is too much chlorine in your hot tub include the following, but it’s a mistake to let it get to this stage!

  • Irritation of the skin or eyes
  • Signs of hot tub components bleaching or being eaten away
  • Vomiting

Is The Smell Of Chlorine A Bad Sign?

One sign that’s popularly taken to mean you’ve put too much chlorine in your tub – the smell that’s commonly associated with the chemical – doesn’t actually normally mean you’ve gone too far.

True, for most people, the smell of what’s called chlorine “off-gassing” is rarely pleasant. It provokes an instant gut response that you’ve made a mistake.

But that smell – commonly associated with badly cared-for swimming pools – is really a sign that the chlorine is doing its job. It’s a by-product of it working.


Chloramines are a chemical waste product created by the oxidisation process through which chlorine beaks down the contaminants in the water.

Contrary to popular belief, the “chorine” smell that the chloramines create is probably a good thing in most cases.


There is an exception though, and that is when adding chlorine to your hot tub for the first time.

In these circumstances, a similar smell can be created by the chlorine reacting with the organic parts of your tub for the first time, creating another chemical compound known as trihalomethanes.

Trihalomethanes also create that off-gassing effect and they’re actually dangerous, so you want to leave plenty of time to allow those levels to balance out before you get in the water.

Add chlorine to your tub, wait, then test

Figuring out how much chlorine to add to your hot tub the first time you use it is always easiest if you properly measure the levels in your water. Don’t be guided by gut instinct or the quantity you put it. Always wait, then test.

This is a good habit to get into to ensure your hot tubbing experience is always relaxing, fun, and healthy for everyone involved.

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