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Spa Sanitizers, Bromine, Mineral Purifier, or Chlorine

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This guide is written to take the mystery out of choosing a sanitizer for your spa. I'm sure you have seen several choices, maybe had experience with some and heard about others. We'll explore three common types of sanitizers and discuss the pros and cons of each.

Using Chlorine as a sanitizer for spas

Chlorine is a halogen, and has been used for many years as a pool sanitizer. It's germ and bacteria killing properties are well documented, and has been the standard in pools for decades. Is it a good choice for a spa? Here are some facts.

Chlorine will begin to offgas, or turn  from a solid to a gas, at 97 degrees. If you keep your spa warmer than 97 degrees, which most of us do, you will need to add more chlorine, more frequently, to maintain a adequate residual. 5 parts per milllion (PPM) is generally accepted as a adequate residual of chlorine in a spa. To maintain this you need to do one of two basic methods. 1) Use solid tablets in a floater. In this method, solid tablets, usually 1" in diameter, are added to a floating dispenser. These dispensers have some method to control how much chlorine is dispensed. This is usually by turning the outside tube of the floater to expose open slots in the inner tube. The more slots exposed, the more chlorine goes into the water.

Using a floater will aide in keeping a even amount of chlorine in the water, and usually only need to be checked every 5 to 7 days. If you find your chlorine residuals are not high enough, you should add additional tablets to the floater, before adjusting the floater to expose more notches. We also recommend shocking the spa with non-chlorine oxidizer shock prior to testing the water by 20 to 30 minutes. This will re-activate any spent chlorine, and give you a more accurate reading of active chlorine in the water. (Chemical name: Potassium Peroxymonopersulphate)

The second method of introducing chlorine to the water is by broadcasting granular chlorine into the spa. Granualar chlorine is readily available, and is relatively inexpensive. The problem with this method is you tend to get a peak and valley effect to the sanitation levels. When you first add the chlorine the levels are very high. They fall quickly due to use and offgasing, and virtually disappear before you add more. During these valleys, or low chlorine levels, bacteria can get a foothold, and start to develope. Once they start it can take as high as 20 times the normal levels, to kill some bacteria. I do not recommend granular chlorine as a stand alone sanitation method for a spa for this reason. Granular chlorine is a excellent addition to other methods and is a excellent product to have around, but if you want to use chlorine in a spa, I recommend the solid tablets and floater method of distribution.

Chlorine pros


Easy to introduce into the water



Dissapates too quickly

Your spa will probably have that typical "Chlorine odor"

Many people are allergic to Chlorine


Bromine is also a halogen, but unlike Chlorine it is more stable in warm water. Therefore it has become the industry standard for spa sanitation. A 3-5 PPM residual is considered adequate for normal usage. Like chlorine, bromine is introduced with a floater. In the same way as described above, the bromine levels can be controlled in your spa. Bromine is not available as a granular product. You may have seen Sodium Bromide sold on Ebay and in retail outlets. This is not Bromine in it's usuable form, but rather it's un-oxidized cousin. Sodium Bromide requires a non chlorine oxidizer such as potassium peroxymonopersulphate, to turn it into bromine. For the same reasons stated above, when we talked about granular chlorine, using sodium bromide and shock can cause the same roller coaster effect to your sanitation levels, and I don't recommend it.

Bromine has a nasty side, and you need to watch the levels carefully. More is not better with bromine. Bromine is acidic and has a very low ph value. It will tend to pull the ph of the spa water down, making it acidic also. Bromine is also a corrosive. If you allow the levels to get too high, it can prematurilly degrade your pump seals and jets, expecially those jets that spin. As with chlorine, I reccommend shocking the water with a non-chlorine oxidizer shock 20 to 30 minutes prior to testing.



Easy to introduce into the water

Stays in warm water better that Chlorine



Easy to loose control of

Low Ph value can lower water's Ph

May get a "Bromine odor" Similar to Chlorine

Many people are allergic to Bromine


The mineral purifier is one of several newer spa sanitation methods. There several types of mineral purifiers, but basically they break down into two catagories. Those that contain silver nitrate, and those that don't. I do not recommend any that do not contain silver nitrate. Without it, they aren't much more than a expensive collection of pebbles and rocks.

Mineral Purifiers were designed as a alternative to more traditional bromine and chlorine. Those with allergies, and those who simply don't want to smell like chlorine when they get out of the spa, now have a viable effective means to sanitize their spa. The minerals are contained in a round cartridge about 4 inches long. These minerals should contain copper and zinc in addition to silver nitrate. You should be able to see copper and zinc nodules in the stick. The theory of operation is the minerals have a affinity for contaminates. They attract and hold the contaminates until a non-chlorine oxidizer shock is added to the water. The oxidizer will change the contaminate into a particle that can be removed by filtration. Those sticks that have silver nitrate have some actual sanitizing power. The romans used silver in their wine to keep bacteria from growing in it as far back as the time of Christ. Copper and zinc have also long been known for their sanitation benifits. It is recommended to add 1 ounce per person, per use of oxidizer shock.

Because the mineral purifier is a relatively non-aggressive means of spa sanitation, it can be overcome easily. Heavy bather load, hot tub parties etc., can overcome the stick. Here is a case where granular chlorine is a good thing to have. 1 tablespoon of granular chlorine will help the stick keep up with the load. You should add 2 ounces of a water clarifier such as spa brite at the same time as the chlorine. Together they will clear the water and restore the effectiveness of the mineral purifier. You don't want to add more chlorine than is necessary, after all  the whole reason to use a mineral purifier, is to stay away from halogens.


No chlorine or Bromine odor

Less dry skin issues thsn Bromine

Solid stick stays in the filter area

Lasts for 4 months

Very few people are allergic to the contents of the stick

Easier on spa components



More expensive to use each stick is $29.99. You use a lot of oxidizer shock at $32.99 per 5 lbs.

Must use Non-chlorine oxidizer shock 1 ounce per person per use

Not as aggressive as Bromine, can be overcome.

Oxidizer shock has a low Ph and will lowewr spa Ph values


All the products I've described are available in my ebay store called Spa chemicals hot tub supplies. (Click this link My ebay store)  I hope this guide has been useful.


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