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Chlorine tablets vs Chlorine granules: which is best for your hot tub?

Chlorine is the sanitiser most hot tub owners choose to keep their water clean and bacteria-free. Over 85% of hot tub owners use chlorine simply because of its cleaning power.

One question we get asked a lot by new hot tub owners is: ‘Should I use chlorine granules or chlorine tablets in my hot tub?’

In this blog, we will go over the main features and benefits of each so you can make the right decision for you.

Chlorine granules are a powdered form of chlorine, designed to dissolve in your hot tub water so they are added directly to your tub. They contain about 60% chlorine (sodium dichlor) so they aren’t as concentrated as tablets.

Chlorine tablets are a bit like dishwasher tablets, small and compact, designed to dissolve much more slowly, and used with a floating dispenser. They contain about 90% chlorine (trichlor) so they are quite powerful which does have certain implications you may need to consider before making your choice.

To help you make your decision, we have broken it down into three things to consider:

  • Cost
  • Control 
  • Chemistry


Even though the cost of chlorine granules has crept up over the last few years, there isn’t much difference between granules and tablets, price-wise.

For 1kg of chlorine granules at Hot Tubs Rock, you will pay £16.99. For 1kg of chlorine tablets, the price is £19.99 so granules work out slightly cheaper.


Both granules and tablets enable you to keep your hot tub water clear, clean, and bacteria-free. Chlorine is excellent for controlling bacteria so it is ideal for keeping your hot tub safe for you and your family to use.

To maintain a healthy chemical balance in your water, chlorine levels should always be between 3-5 ppm (parts per million). Too little chlorine and nasty bacteria can grow; too much chlorine will give you red, itchy skin and eyes. That’s why regularly testing your water with testing strips to keep within that range is vital for the health of your hot tub, and more importantly, the health of anyone getting in.

Chlorine tablets are great because they slowly dissolve, topping up the chlorine as needed. However, it is possible to get a little complacent, thinking that just because you have chlorine tablets in your floating dispenser, the chlorine levels are fine. This is not always the case, which is why regular testing is so important.

This is less likely to happen if you use chlorine granules because how much you add to the water will be based on the results of testing using a testing strip. There is more measuring out of granules to do but on the flip side, you will not fall into the trap of ‘fill the dispenser and forget’.


Both granules and tablets impact the overall chemical balance of your hot tub water. How they impact your water chemistry will help you decide what’s best for you and your hot tub.

Chlorine tablets have a higher concentration of chlorine in them (roughly 90%) – they are acidic by nature. As the tablets slowly dissolve into your water, they do affect the pH and alkaline levels of your water. Over time, if not addressed, this can lead to unhealthy water, resulting in red, itchy eyes and skin.

Using tablets also means that you must make sure you remove the floating dispenser from your tub before hopping in because, if handled, they can irritate your skin.

Chlorine granules, on the other hand, have a much lower concentration of chlorine in them (about 60%) so they do not affect the pH and alkaline levels of your water nearly as much. Also, there is no issue with skin irritation with granules, you just measure them out, put them in your water and you are good to go.

So, to sanitise your hot tub water, there are arguments for using tablets and granules. Tablets are a little more expensive and much more convenient – you just pop them into your floating dispenser and that’s it. 

However, if the convenience of using a floating dispenser is likely to lull you into a false sense of security, then using granules as part of your regular testing may be the way to go.

Either way, as long as you keep your chlorine levels between 3-5ppm at all times then your hot tub water will always be clean and clear, and perfectly healthy for you to slip into whenever you need it.

Please check out our range of chlorine granules, tablets, testing strips, and everything else you need in our shop to maintain your hot tub water.