Bromine vs. Chlorine

Bromine vs. Chlorine

Bromine or Chlorine?

There are two types of sanitizers that one could use in a swimming pool – Bromine or Chlorine. Both are members of the Halogen family of elements, nestled between Fluorine and Iodine on the periodic table.

Bromine and chlorine are close cousins of each other, but they have distinct personalities, as cousins often do, and behave differently in many ways.

Bromine and chlorine each have their own pros and cons...

Bromine Advantages

  • More stable at higher temperatures than chlorine
  • More potent at higher pH levels than chlorine
  • Bromides are reactivated by superchlorinating
  • Bromamines are still active sanitizers, with low odor
  • Adds no cyanuric acid or calcium to the water

Bromine Disadvantages

  • Bromine tablets are more expensive than chlorine
  • Bromine is not as widely available as chlorine
  • Bromine is not as effectively stabilized from the sun

Chlorine Advantages

  • More widely available than bromine
  • Much cheaper than bromine, up to 40% less
  • Can be stabilized from the sun with cyanuric acid
  • Higher percentage of available sanitizer

Chlorine Disadvantages

  • Chloramines are weak sanitizers and gas-off more readily
  • Less effective at high pH levels above 7.8
  • Stabilized chlorine products add cyanuric acid, which can rise too high
  • Warm or hot water temperatures rapidly depletes chlorine

Can Bromine be used with Mineral Purifiers?

Nature2 is a mineral sanitizer that uses silver and copper ions to help purify a spa or pool. Other similar mineral purifier products are made by Frog, Leisure Time and others.

There is a bit of misinformation online regarding the use of Bromine and Mineral Purifiers. If you ask the question to a search engine, “Can Nature2 be used with Bromine?”, you will find a lot of negative responses, stating that Nature2 is incompatible with Bromine. But other mineral purifiers, which are essentially knock-offs of the Nature2 technology, state that either bromine or chlorine can be used.

Searching the Zodiac website, the only information about incompatibility is that Nature2 should not be used with Biguanide products or copper algaecides, but nothing about bromine. In a phone call to Zodiac tech support, I was told that they recommend use with chlorine only because that’s the only halogen that was tested and evaluated by the EPA. Bromine use in conjunction with Nature2 has not been evaluated or registered, and therefore is not recommended by Zodiac.

However, you can use bromine with mineral purifiers, yes.

Can Bromine be Stabilized?

Outdoor pool owners that use chlorine are familiar with cyanuric acid, sold as pool “conditioner” or “stabilizer”. Pool chlorine tablets, “Trichlor Tabs” also have cyanuric acid added to the tablet. A level of 30-50 ppm of cyanuric acid is recommended in outdoor pools, to help protect chlorine from the sun. Bromine is commonly not used in outdoor pools, especially sunny outdoor pools, because it traditionally cannot be stabilized or protected from the sun.

However, bromine tablets, made with BDMCH are in a class of sanitizers known as halogenated hydantoins. When chemists began adding hydantoins to bromine, the result of slower release, or time release was noted, in addition to reduced degradation by sun and heat. However, bromine is still susceptible to UV degradation in sunny outdoor pools, but cannot be stabilized like chlorine.

Do I need to use twice as much Bromine as Chlorine?

A small amount more bromine is usually needed, as compared to Trichlor tablets. This is because Trichlor tablets are usually 90% available chlorine, whereas Bromine tablets are just under 70%. Thus, pound for pound, chlorine is more potent. However, chlorine also dissolves more quickly than bromine, and is more active, which results in more rapid dissipation.

The perception that one would need twice as much bromine as chlorine likely comes from the fact that users of bromine are advised to maintain a level of 2-4 ppm of bromine, while with chlorine only 1-2 ppm is recommended. This does not mean that you need twice as much bromine, but it’s because bromine is 2.25x heavier than chlorine, and when using a chlorine test kit, the reading is multiplied by 2.25, or a darker comparison color chart is used.

Is there a test kit for Bromine?

Testing for bromine is accomplished with the use of a chlorine test kit, or a DPD test kit. There are test kits labeled as “Bromine Test Kit”, but they are simply chlorine test kits, slightly modified for use with Bromine. If you are using a chlorine color comparison chart with test strips, or matching colors with a test kit comparator for chlorine, multiply the result by 2.25 to convert a chlorine test to a bromine test.

Will Bromine bleach swimsuits or clothes?

Yes, but probably not to the same degree as chlorine. Bromine is less active than chlorine, and even though the levels of bromine may be higher, the bleaching effect on swimsuits and skin irritation is generally less.

Does Bromine affect pH level?

Bromine has a low pH of around 4, and using bromine tablets will slowly lower pH and alkalinity over time, requiring additions of a base chemical to raise pH and alkalinity. The same can be said for chlorine tablets, which have a pH even lower, around 3.

Bromine is far less affected by pool or spa water pH than chlorine, and able to be an active sanitizer at high ph levels of 7.8 – 8.2.

Can Bromine be used in pools?

Yes it can, however in a sunny outdoor pool it may burn off quickly, since bromine is not stabilized from the sun in the same way as chlorine.

Indoor pools however, can use bromine very effectively. Some pool operators enjoy the reduced effect of disinfectant byproducts, including bromamines. Indoor pools that use chlorine may need to frequently shock the pool to reduce chloramine levels, which can foul the air and cause corrosion to metal items around the pool, and air handling equipment. Outdoor pools with automatic pool covers could also use bromine effectively.

Bromine is known to have a less pungent smell, even when combined with ammonia or nitrogen. Combined bromine, or bromamines also remain a viable (although slightly less potent) sanitizer.

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