Hot Tub Bromine Granules BDCMH

Fast-acting bromine granules for hot tubs and spas. A BCDMH-based granular sanitiser that establishes a bromine bank, then keeps the water gentle on bather skin and stable through wide pH swings.

Establishes a bromine bank for ongoing sanitisation.
Sanitises through wider pH band (7.0-7.8) than chlorine.
Stays effective at hot-tub temperatures up to 40 C.
Forms fewer eye-stinging by-products than chlorine.
Works alongside Bromine Tablets 20g for steady ongoing dose.

Sizes and prices

1kg: £16.18
2.5kg: £28.33
5kg: £48.58
10kg: £89.09
20kg: £170.10
25kg: £210.60

When you need it

You are starting a new bromine system from fresh water.
You want a sanitiser that is gentler on sensitive skin.
You need a fast top-up after a heavy soak.
Bromine reading has dropped below 3 ppm.
You want a sanitiser that holds steady at 38-40 C.

How to use

Test bromine, pH and total alkalinity with a fresh kit.
Balance pH to 7.2-7.6 and alkalinity to 80-120 ppm before dosing.
For a fresh fill, dose 25 g per 1000 L pre-dissolved in 5 L of warm water.
Switch jets on full and pour the solution evenly across the surface.
Run circulation for 60 minutes; retest bromine.
For top-ups, dose 5 g per 1000 L when bromine reads below 3 ppm.

Dosing guide

Initial bank establishes the bromide reserve; top-ups maintain the active bromine band. Expect to redose top-ups every 2-4 days depending on bather load.

For 1,000 L, add 25 g to reach Initial bank.
For 1,500 L, add 37 g to reach Initial bank.
For 2,000 L, add 50 g to reach Initial bank.
For 1,000 L, add 5 g to reach Top-up.
For 1,500 L, add 8 g to reach Top-up.
For 2,000 L, add 10 g to reach Top-up.

How it works

Bromochlorodimethylhydantoin (BCDMH) granules with at least 60% available halogen. The granules dissolve to release both bromine and a small chlorine activator that recycles spent bromide back to active bromine.

BCDMH dissolves to release hypobromous acid (HOBr), the active sanitiser. As it kills bacteria and oxidises waste, HOBr converts to bromide ion. The chlorine fraction in BCDMH then re-oxidises bromide back into HOBr, sustaining the bromine bank with much less product than chlorine alone.

Bromine remains active in the warm, slightly alkaline conditions where chlorine struggles. Hot tub water held at 38 C burns off chlorine 3-5 times faster than bromine. Bromine is the standard professional choice for spas and high-temperature pools.

Frequently asked questions

What is the ideal bromine level?

3-5 ppm for hot tubs and 2-4 ppm for indoor pools.

How often should I dose?

Top-up every 2-4 days; weekly initial bank refresh after a water change.

Can I bathe straight after dosing?

Wait until bromine reads below 8 ppm; usually 30-60 minutes after dosing.

How long does 1 kg last?

Approximately 5-6 months of top-ups for a 1500 L hot tub.

Are bromine granules safe for sensitive skin?

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

Should I use granules or tablets?

Granules are for fast top-ups and the initial bank; tablets are for slow daily release. Most users run both together.

What is the active ingredient?

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

Why do bromine systems need a bank?

Bromine cycles between active HOBr and spent bromide. The bank is the bromide reserve that the chlorine fraction in BCDMH continually re-oxidises.

Does bromine raise total dissolved solids?

Yes. Heavy long-term dosing pushes TDS up; refresh the water when TDS exceeds 1500 ppm.

Bromine not climbing?

Raise pH to 7.4 and dose the initial bank rate.

Strong bromine smell?

Shock with MPS at 17 g per 1000 L; ventilate for 30 minutes.

pH drifting up?

Dose pH minus weekly; bromine systems run higher pH than chlorine.

Bromine granules vs tablets?

Granules dissolve fast for instant top-ups. Tablets give a slow, steady release. Use both together for stable hot tub care.

Bromine vs stabilised chlorine?

Bromine is gentler at hot tub temperatures. Stabilised chlorine is more cost-effective for outdoor pools with heavy UV.