Chlorine granules vs chlorine tablets: Which is better for your hot tub?

Posted by Nick Clamp in Maintaining a Hot Tub Guides on 21st March 2022

Chlorine is the sanitiser of choice for most hot tub owners as it’s affordable, widely-available, and easy to use.

But which is better: chlorine granules or chlorine tablets?

The fact is that both come with their own pros and cons. Read on to find out which is the best option for you.

How do chlorine granules work?

Chlorine granules dissolve as soon as they’re added to your hot tub’s water, giving it an immediate free chlorine boost. Your chlorine levels will then begin to slowly drop from this point – and you’ll need to top your tub up with more granules when they fall below 3mg/l (milligrams per litre).

How do chlorine tablets work?

Chlorine tablets are added to a floating dispenser and dissolve slowly over time. Instead of giving your hot tub a big chlorine boost all at once, they gradually feed chlorine into the water, keeping the free chlorine levels steady until they completely dissolve and need replacing.

Which is cheaper?

Chlorine granules and tablets cost about the same when it comes down to it, which means price isn’t really a deciding factor when it comes to picking which is right for you. 

Which is easier to use?

There isn’t much in it when it comes to whether chlorine granules or tablets are easier to use – although tablets probably just edge it.

Here’s why:

If you opt to use chlorine granules, you’ll have more control over your hot tub’s free chlorine level but will need to be more proactive about keeping it in the right range. As soon as you notice your chlorine levels have dropped below 3mg/l (milligrams per litre) during the checks you make as part of your regular hot tub maintenance routine you’ll have to top them up manually by measuring out the right amount of granules and then adding them to your tub.

If you go with chlorine tablets, your spa’s free chlorine levels are unlikely to drop below 3mg/l until your tablets are gone, since they slowly release chlorine until they run out. Once the tablets have dissolved, you simply need to add more to the dispenser and forget about sanitiser levels until the next time they run out.

However, while chlorine granules have a relatively neutral pH, hot tub tablets are quite acidic. That means they’ll drive down your hot tub’s pH if left unchecked, which can lead to serious headaches. Plus, your hot tub’s chlorine levels are a lot harder to control with tablets. That means you might find your hot tub chemistry harder to put right if it ever goes awry.

Because they’re “set it and forget it”, chlorine tablets are easier to use. However, they make it harder to keep your hot tub’s pH balanced and give you less control over its free chlorine levels, which which means they’re possibly better suited to someone who’s well-versed in hot tub chemistry.

Which is more effective?

As long as you’re checking your sanitiser levels each day and adjusting them when necessary, chlorine granules and tablets are equally effective at keeping your spa clean and hygienic. 

If you know you’re liable to forget to check your sanitiser levels every day then tablets are probably the way to go, as they’re more forgiving if you miss a check here and there.

However, it’s worth noting that chlorine releases gases when it dissolves in water. If you don’t remove your spa’s cover for days on end these will build up if you’re using chlorine tablets and can discolour components like headrests.  

So, while chlorine tablets are more forgiving if you forget to check your hot tub’s sanitiser levels every now and then, you’ll still run into problems if you leave your home spa untouched for days at a time.

Which makes it harder to keep your hot tub chemistry balanced?

Because they’re acidic, chlorine tablets have a much bigger impact on your hot tub chemistry than relatively neutral granules. This isn’t much of a problem if you’re checking your pH levels every day as part of your home spa maintenance routine – it just means you’re going to have to reach for the pH increaser more often than if you were using granules. 

However, it’s worth keeping in mind that chlorine tablets can quickly cause problems with your pH levels if you fall out of the habit of testing your hot tub’s water every day. 

How to eliminate chlorine odour from your hot tub

Both chlorine granules and tablets produce chlorine odour. 

That’s because, whichever form it comes in, chlorine creates hypochlorous acid when it dissolves in water which is what kills bacteria and sanitises your spa. Once this hypochlorous acid has reacted with other elements, it deactivates and leaves behind chloramines, which are what create that distinctive swimming pool smell.

Luckily, there’s an easy fix if the chlorine odour gets so strong that it starts spoiling your soaks: shocking your hot tub. This will help eliminate the nasty byproducts chlorine leaves behind and leave you breathing easy.

Which is better: chlorine granules or chlorine tablets?

Chlorine granules and tablets both come with their own set of pros and cons, and which is right for you really comes down to a matter of preference.

For some people, topping their hot tub up with chlorine granules when a test strip tells them its free chlorine levels are too low is the easiest way to keep it clean and hygienic. Other people prefer the “set it and forget it” nature of tablets, even though that means spending a bit more time and energy balancing their spa’s pH.

When it comes down to it, both chlorine granules and tablets are an easy and affordable way to sanitise your home spa and you can’t go wrong with either.

After more hot tub maintenance tips? Grab your free copy of the latest edition WhatSpa? magazine for our tips and tricks on how to get the most from your home spa, as well as our picks of the best buys for every budget.

About the author

Nick Clamp

I am the Editor-in-Chief at WhatSpa? Media Group and my job is to keep you informed about the very latest hot tubs on the UK market... the best job in the world! When I'm not being deluged with press releases and hot tub brochures I enjoy keeping fit and participating in endurance events including triathlons and distance running.

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