# Chlorine tablets vs granules for hot tubs

Source: https://bubbleandsoak.co.uk/blog/chlorine-tablets-vs-granules-hot-tub
Published: 2026-10-12
Publisher: Bubble and Soak

**In short:** Granules dissolve fast, so you can raise chlorine quickly and adjust the dose after each test. Tablets dissolve slowly in a floating dispenser, keeping a steady trickle of chlorine between soaks but making quick changes harder. Many owners use granules as the main dose and after heavy use, and some add a tablet dispenser for top-up. Always follow the product label.

Chlorine for hot tubs comes in two main forms: small granules you measure out with a scoop and larger tablets that sit in a floating dispenser. Both usually contain stabilised chlorine, and both can keep an inflatable tub sanitised. They differ in how fast they work and how much control you have. This article compares them so you can choose a routine, and explains why tablets made for swimming pools are not always suitable for a hot tub.

## How each form works

Chlorine granules are measured into the water, usually with the pump running so they mix and dissolve. They act quickly, so a test a short while later shows the effect. That makes them good for setting the level after a refill and for topping up after a busy session.

Chlorine tablets dissolve slowly over days. In a hot tub they go in a floating dispenser, never loose on the floor of an inflatable, because a tablet resting on the liner can damage it. Some hot tub tablets are small multifunction tablets that combine chlorine with other agents. The dispenser's vents control how fast they dissolve.

## Side by side

| Point | Granules | Tablets in a dispenser |
| --- | --- | --- |
| Speed | Fast acting | Slow and steady |
| Control | Easy to adjust the dose | Adjust by opening or closing the vents |
| Best for | Start up, after use, correcting low levels | Keeping a baseline between soaks |
| Risk | Overdosing if not measured | Too high or too low if vents are not set well |
| Liner safety | Pre-dissolve or add with pump running | Never let a tablet sit on the liner |

Chlorine granules and tablets compared

## Getting the dose right

Whichever form you use, the aim is a free chlorine level in the range given on your test strips and product label, often around 1 to 3 ppm for hot tubs. Test before and after dosing until you know how your tub behaves. Our guide to [reading test strips](https://bubbleandsoak.co.uk/blog/how-to-read-hot-tub-test-strips) explains the colours.

Dose is always set by the product and your water volume. Use our [water volume calculator](https://bubbleandsoak.co.uk/tools/water-volume-calculator) to find your litres, then follow the label. Our [chemical dosing page](https://bubbleandsoak.co.uk/blog/hot-tub-chemical-dosing-chart) has a worked example.

## Pool tablets are not hot tub tablets

Large chlorine tablets sold for swimming pools are often trichlor, which is acidic and very concentrated. They can push pH down quickly in a small volume of hot water. Use products labelled for hot tubs or spas, and check whether your tub's maker recommends a type.

Never mix different chlorine products or chlorine with bromine products in their dry form, and store all chemicals in a cool, dry place out of reach of children.

Note: Read the label before using any hot tub chemical. Add chemicals to water, never water to chemicals, wear gloves if advised, and keep products in their original containers away from children.

## A simple routine using both

If tablets keep pushing chlorine too high, close the vents or remove the dispenser between uses. See [how to lower chlorine](https://bubbleandsoak.co.uk/blog/how-to-lower-chlorine-in-a-hot-tub) if you overshoot.

1. After refilling, balance pH and alkalinity, then raise chlorine with granules to the label's start up level.
2. Set a floating dispenser with tablets to hold a baseline, if your maker allows one.
3. Test before each soak and add granules if chlorine is low.
4. After a busy session, add a granule dose and leave the cover open for a short while.
5. Adjust the dispenser vents if levels keep creeping up or down.

## Which should you choose?

For most inflatable tubs, granules give the control you need, especially with irregular use. A tablet dispenser suits owners who soak often and want fewer top-ups. Keep it simple and stick with one chlorine type rather than swapping often. If you prefer bromine, see [chlorine vs bromine](https://bubbleandsoak.co.uk/blog/chlorine-vs-bromine-inflatable-hot-tub).

[Find an inflatable hot tub](https://bubbleandsoak.co.uk/best/best-inflatable-hot-tubs)

## Frequently asked questions

**Can I put chlorine tablets straight into my inflatable hot tub?** No. A tablet sitting on the floor can bleach and weaken the liner. Use a floating dispenser or the maker's own dispenser.

**Are multifunction tablets enough on their own?** They can keep a baseline, but most owners still need granules after heavy use or a refill. Test regularly and follow the label.

**Can I use pool chlorine in a hot tub?** Products made for pools may be stronger or more acidic than suits a small, hot volume of water. Use spa products where you can.

**Do granules or tablets affect pH?** Some forms of chlorine affect pH more than others. Test pH regularly and correct it as needed.

## Buying guides on this topic

- https://bubbleandsoak.co.uk/best/best-inflatable-hot-tubs
- https://bubbleandsoak.co.uk/best/lay-z-spa-models-compared
- https://bubbleandsoak.co.uk/best/best-2-to-4-person-inflatable-hot-tubs