Chlorine is an excellent antimicrobial and disinfectant agent for use in swimming pools. A well-maintained swimming pool is treated with chlorine at 1-to-3 ppm (parts per million.) This keeps the pool clean and safe for swimming.
For the purpose swimming pool use, "chlorine" is not your basic liquid bleach like Clorox® Bleach, but a specific chlorinated chemical. Usually one of either Sodium Dichloro-S-Triazinetrione (granular) and Trichloro-S-Triazinetrione (tablets or sticks.) "Chlorine" in this article shall refer to one or either of these cited chlorinated agents.
A disadvantage of chlorine is that once encounters bacteria or other undesirable contaminants in pool water (e.g., mold, algae, parasites, etc.) it bonds to the contaminant and loses much of its effective strength.
Molecules of chlorine have become 'bound up' in this process and must over time, be replaced. This is why it is advised for swimmers and bathers to shower immediately before entering a pool. This reduces the debt-load introduced to this balanced system and makes the available chlorine last longer.
Over time, additional chlorinated pool chemicals must be added to maintain the correct pH levels. Even at the required 1-3ppm (parts per million) concentration of chlorine, the effective strength poses a problem for people with sensitive skin. Another disadvantage of chlorine when a pool is fully chlorinated is that it causes metallic ions (iron, manganese, nickel and copper, etc.) that are naturally present in the water to penetrate their hair, giving light-colored hair, especially blond hair, a greenish tint (See article: "Help! My Hair is Green ~..." for details.)
Bromine used for Swimming Pools
The chemical bromine is very similar in properties to chlorine, and is often used in conjunction with chlorine. Not a replacement for chlorine, bromine also kills bacteria and algal growth in swimming pool water.
Bromine is more heat-stable than the normal chlorinated pool chemicals and is more suitable for hot-tub and spa use, but it is also used in unheated pools.
A static delivery device for bromine introduction for home pool/hot tub use is typically used; a floating buoy containing a commercially-available bromine tablet. Bromine is also administered to larger pools and spas via a granular form for quicker stabilization.
Can Bromine Replace Chlorine in Pools, Hot Tubs and Spas?
Bromine offers advantages over its chlorinated cousin in that there is less of an odor and less of a skin irritant. While bromine use cannot completely replace chlorination chemicals in pools, the use of a bromine table can reduce the required amount of chlorine.
Bromine also has the advantage that after it attaches to the contaminant, it is liberated again with the weekly 'shock' that pools require. Much of the bromine returns to the pool water after the contaminants are 'burnt off' with the required 'shock treatment.'. Weekly shock treatments remove the accumulated load of inactivated bacteria and contaminants but the chlorine that did the job is also removed via the filters and must be replaced.
A Disadvantage of Bromine for Pools
The biggest single advantage of bromine use for pools and hot tubs is cost: bromine is quite expensive versus the lower cost chlorinated chemical. For the hot tub owner however, bromine should be used because it is more heat-stable and thus, more effective at sterilizing and maintaining safe and correct water pH.