The single most important additive to your hot tub water is a sanitizer. It is imperative that a proper level of sanitizer be maintained to effectively disinfect your spa water to prevent illness or discomfort. A variety of spa sanitizers are available with the most common being bromine and chlorine. Following is a description of a few different types along with their respective advantages and disadvantages.


Bromine is a member of the chemical family of halogens which includes chlorine. They kill bacteria by destroying the enzymes and structures inside the microorganism's cells, rendering them harmless. In our area of overnight cabin rentals, bromine is used nearly exclusively. It is relatively inexpensive to use and is easy to maintain in the proper level by using tablets in a floating dispenser. Unlike chlorine which has no further sanitizing capability once combined with waste, bromine can be reactivated with a non-chlorine spa shock. It has a less offensive odor and causes less drying out and itching of the skin than chlorine. Bromine is more pH stable but this also makes it more difficult to remove any residual odor from your skin. Bromine levels should be maintained in the 3.0 to 5.0 PPM range. To assure initial effectiveness, granular sodium bromide should be added at startup to establish an immediate bromine bank.


Convenient to use/inexpensive

Readily available

No difference between the effectiveness of free versus combined bromine

Less odor than chlorine

Less skin irritation than Chlorine


Low pH (approx. 3.5 to 4.5)

Bromine odor more difficult to shower off

Requires the use of sodium bromide when water is changed to establish an immediate bromine reserve


Chlorine is also a member of the chemical family of halogens. It is inexpensive, very effective and fairly easy to use. Chlorine has to be added to a hot tub frequently because it has no sanitizing ability once it combines with waste. Chlorine also has a strong smell that some bathers may find unpleasant and it has a tendency to dry out skin leading to itching and possibly rashes. Chlorine levels should be maintained in the 1.5 to 3.00 PPM range.


More neutral pH - sodium di-chlor has a pH of 7.0

Readily available

Can be used as both a sanitizer and a shock



Less convenient - needs to be added manually several times a week

Confusing varieties - Numerous types of chlorine are available. Only sodium di-chlor should be used in hot tubs

No sanitizing ability after it combines with waste

Strong odor/skin irritation

Some tub manufacturer's may void warranty if used

Mineral Purifiers

Natural mineral purifiers incorporate silver and copper to naturally destroy contaminants that create cloudy water. They work in conjunction with your chlorine spa sanitizer, reducing the amount needed by half or more (can be reduced to only 0.5 PPM). They do not function as a sanitizer by their selves. While they will save you money for sanitizer, they only last for about four months.


Easy to use, fits inside filter

Lasts up to 4 months

Can be used with chlorine and ozone

No chemical smells


Need to shock frequently with chlorine or non-chlorine spa shock

Only last 4 months

Some brands (Nature 2) cannot be used with bromine, biquanides or other products containing copper

Cost/difficulty finding product


Biquanides (chemical name: polyhexamethylene biquanide or PHMB) are sold under brand names such as Baquacil® and SoftSwim®. We do not stock any of these products because they are incompatible with other spa chemicals, are much more expensive than other sanitizers and usually require additional unique products such as special filter cleaners, etc. They also may attack some plastics such as polycarbonates.


Easy to use, add once a week

No chemical smells

No bromine/chlorine skin reactions


Very expensive/hard to find

Can discolor or eat some plastics

Some tub manufacturer's may void warranty if used

Filter cleaning much more involved

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