Hot Tub Bromine Tablets 20g - Slow Dissolving

What is a bromine tablet and what is it used for?

A bromine tablet is a slow dissolving sanitiser tablet used to keep hot tub water clean. It releases bromine into the water over time, helping maintain a steady sanitiser level between top ups and routine water care checks.

For most UK hot tub owners, bromine tablets are used as part of a simple weekly routine. They are usually placed in a floating dispenser or the spa's tablet feeder so the dose can dissolve gradually, rather than being added loose into the water.

Used for ongoing hot tub sanitising, not for one off shock treatment
Best added through a floating dispenser or built in feeder
Helps maintain day to day bromine levels between water tests
Commonly paired with regular pH checks and occasional shock treatment when needed

How to use bromine tablets in a hot tub

Before adding a bromine tablet, test the water and make sure pH is in the correct range for your spa care routine. Then place the tablets into a floating dispenser or feeder and adjust the openings so they dissolve at a steady rate. The exact number needed will vary by spa size, water temperature and how often the hot tub is used.

Check the water regularly and top up the dispenser before it runs empty. If the hot tub has had heavy use, cloudy water or a fresh refill, you may also need separate water balance products or a shock treatment as part of normal maintenance.

Do not place bromine tablets directly onto the shell surface
Do not mix bromine tablets with other chemical types in the same feeder or container
Store tablets in a cool, dry place with the lid closed
Keep out of reach of children and always follow the product label instructions

Slow-dissolving 20 g bromine tablets for hot tubs and spas. Dropped into a floating dispenser they hold 3-5 ppm bromine for 1-2 weeks per dose, ideal for low-effort weekly maintenance.

Holds free bromine at 3-5 ppm for 1-2 weeks per dose.
Dissolves slowly through a floating dispenser or erosion feeder.
Stays active across pH 7.0-7.8 and temperatures up to 40 C.
Forms fewer skin-irritant by-products than chlorine.
Pairs with Bromine Granules for fast top-ups.

Sizes and prices

1kg: £18.47
2.5kg: £33.79
5kg: £59.33
10kg: £110.40
20kg: £212.55
25kg: £263.62

When you need it

You want a low-effort weekly hot tub regime.
Bromine reading has fallen below 3 ppm.
Sensitive skin in the household reacts to chlorine.
Water temperature is held above 38 C for long periods.
You want a sanitiser that holds through pH drift.

How to use

Ensure your hot tub is clean and filled with fresh water.
Test pH and alkalinity; balance to pH 7.2-7.6 and TA 80-120 ppm.
Place 1-3 tablets per 1000 L into a floating dispenser or erosion feeder.
Adjust dispenser ports to release evenly over 7-14 days.
Test bromine after 24 hours; aim for 3-5 ppm.
Add or remove tablets to maintain band; shock weekly with MPS.

Dosing guide

Adjust based on bather load and water temperature. Heavy use or hot weather may require an extra tablet or a wider dispenser opening.

For 1,000 L (small spa), add 1-2 tablets to reach Standard.
For 1,500 L (typical hot tub), add 2-3 tablets to reach Standard.
For 2,000 L (large hot tub), add 3-4 tablets to reach Standard.
For 5,000 L (swim spa), add 8-10 tablets to reach Standard.
For 1,500 L, add 3-4 tablets + weekly MPS shock to reach Heavy use.

How it works

Bromochlorodimethylhydantoin (BCDMH) compressed into 20 g slow-release tablets. Each tablet contains at least 60% available halogen and is engineered to dissolve evenly over 1-2 weeks in a dispenser.

BCDMH releases hypobromous acid (HOBr), the active sanitiser, plus a small chlorine activator. The chlorine recycles spent bromide back into active bromine, sustaining the bromine bank with very little product compared to dosing chlorine alone.

Bromine remains active above 38 C, where chlorine is destroyed quickly. The slow-release tablet form hands you a full week of stable sanitiser without daily intervention, the standard professional approach for hot tubs.

Frequently asked questions

How long do the tablets last in a dispenser?

Depending on the flow rate and water temperature, the tablets typically last 1-2 weeks before needing replacement.

Can I use these in my inflatable hot tub?

Yes, these are perfectly safe and effective for inflatable hot tubs when used in a floating dispenser.

How many tablets do I need for my tub?

As a general rule, use 1-3 tablets per 1000 litres of water, adjusting based on regular testing to maintain 3-5 ppm.

How long does a 1 kg pack last?

50 tablets at 20 g each, around 4-6 months for a typical 1500 L hot tub.

Are they suitable for sensitive skin?

Yes. Bromine forms fewer skin-irritant by-products than chlorine and is the standard choice for sensitive bathers.

Will they work in a salt-water spa?

Use only when the salt cell is offline; bromine and salt chlorination are not run together.

What is the active ingredient?

Bromochlorodimethylhydantoin (BCDMH) at >= 60% available halogen.

Why is bromine better at high temperature?

Bromine remains stable above 38 C while chlorine is destroyed quickly. Hot tubs need a sanitiser that survives the heat.

Do I still need to shock?

Yes, weekly with Non-Chlorine Shock to clear combined bromine and restore active bromine bank.

Bromine reading low?

Open dispenser; dose Bromine Granules to refresh the bank.

Strong bromine smell?

Shock with MPS; ventilate for 30 minutes.

Tablets vanishing too fast?

Close dispenser ports; check water temperature is within range.

Bromine tablets vs chlorine tablets?

Bromine handles heat better and is gentler on skin; chlorine is cheaper but burns off faster at hot tub temperatures.

Bromine tablets vs bromine granules?

Tablets give slow steady release for low-effort care; granules give fast top-ups when bromine has dropped.