Some people use chlorine granules or tablets, some use bromine, but most people in the UK use chlorine granules for hot tub cleanliness.

Here’s everything you need to know about why you’ll probably want to join other hot tubbers in using chlorine granules and how to use them when you do.

What Are Hot Tub Chlorine Granules?

Hot tub chlorine granules are a fast-dissolving powdered form of chlorine that you commonly add to your hot tub water half an hour or so before use in order to kill bacteria.

Technically speaking, most chlorine granules consist of sodium diclor (full name sodium dichloroisocyanurate, but that’s a bit lengthy so you’ll usually see it abbreviated) made by combining chlorine with cyanuric acid.

There are other types of granules used in hot tubs, but sodium diclor is the longest-lasting option and the most common form of chlorine granules.

Why use chlorine granules in your hot tub?

1) Easy to use

Using chlorine granules is as simple as adding them to the water in your hot tub. All you need to know are a few basics.

The alternative is chlorine tablets used in a floating chlorine dispenser. These coin-sized tabs are placed in the dispenser and left in your tub to slowly dissolve over time.

Both are pretty easy to use. But as many tablet-using hot tubbers find themselves using granules to balance chlorine levels anyway, simply using them in the first place can be the best strategy.

2) Control bacteria and cleanliness

There’s a reason why chlorine is pretty much omnipresent when we’re trying to control bacteria in all kinds of environments – it works.

In hot tubs, chlorine granules give you maximum ability to adjust the chlorine levels in your water. This needs to be between 1.5 and 3 parts per million to prevent bacteria growth.

There’s an argument that says placing chlorine tablets in a dispenser and letting them do their thing is easier. After all, it’s easy enough to forget to top up your tub’s chlorine levels if you’re using granules. Tablets are essentially fire-and-forget.

However, using granules makes it much easier to adjust levels than slow-dissolving tablets. Granules also encourage you to get into the habit of testing your levels regularly, which is a very good thing.

3) Create balanced, pleasant water

Sodium diclor chlorine granules are fairly pH neutral, meaning they won’t upset your hot tub water chemistry very much.

Chlorine tablets, on the other hand, are actually trichloroisocyanuric acid. This can unbalance the levels of your water, causing itchiness and red eyes if you let it get out of hand.

The far lower impact of granules on your hot tub’s acid-alkaline chemistry balance makes them a superior choice for pleasant ‘tubbing conditions.

How to use chlorine granules in your hot tub – FAQs

How many chlorine granules should I put in my hot tub?

You want to make sure you always have the right sanitiser levels in your tub. Guidelines for this vary by manufacturer. For example, Lazy Spa chlorine granules say you’ll need 2g of granules to raise every 1000 litres of water in your tub by 1 ppm.

You can measure this quickly and easily with a teaspoon. A level teaspoon of granules is said to be around 5g. (As you can imagine, this level of dosing means that a standard 5kg chlorine granule tub lasts for a long time!)

How do I add chlorine granules to my hot tub?

You’ll normally want to add chlorine to your hot tub a little at a time. Go too far and you’ll over-chlorinate and have to wait before you can get in!

• Water temperature over 20°C – simply sprinkle chlorine granules into the water.
• Water temperature under 20°C – pre-dilute chlorine in a plastic container of warm water before adding.

How long after putting chlorine granules in a hot tub can you use it?

Always give it at least 30 minutes between putting chlorine granules in your tub and using it. Make sure you leave the cover off the tub so any vapour can escape.

There is also so-called “shock dosing” when you need to quickly raise chlorine levels from zero. You’ll want to do this about 24 hours in advance of use though, as you’ll need to let the levels sink to that comfortable 1.5 to 3ppm before you sink into your tub.

Should I put chlorine in my hot tub every day?

Almost certainly not. You’ll want to work to a set level (1.5-3 ppm) rather than a schedule, which you’ll find equates to around twice or three times per week. Again, with a 5 kg chlorine granule bag you’ll have enough to last for a while!

It’s worth making the small amount of effort it takes to test your chlorine levels often. Too low, and your risk bacteria forming. Too high (over 3 ppm), and you risk itchy skin and red eyes. Over 5 ppm and you risk chlorine poisoning (you really don’t want this!).

With a little care though, using chlorine granules for hot tub cleanliness is the best way to keep your water fresh, healthy, and ready to be enjoyed.

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