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The most common way to sanitize or disinfect a pool and spa

The most common way to sanitize or disinfect a pool and spa is through the use of chlorine compounds. Chlorine is a member of the halogen family of elements and the other members, bromine and iodine, can also be used in disinfection. Bromine is commonly used in hot tubs.

The chemistry of bromine is similar to but less reactive than that of chlorine. It can not be used as shock. Bromine as an element is a brown volatile liquid that has irritating toxic fumes. For use in pools and spas it is used in solid form as a salt with an accompanied oxidizer or as a tablet or stick that contains both the bromine and the oxidizer.

Bromine, like chlorine combines with organic material. These combined forms are still effective sanitizers. The combined bromamines unlike chloramines do not smell. For this reason some people prefer bromine compounds for spas.

Iodine is also a sanitizer but it is usually not used for pools and spas because it only gives bacteria free water and it is necessary to use an additional oxidizing agent for algae and organic matter. Its good points are that it is non-irritating and does not bleach hair and bathing suits.

Ozone has been used for over 100 years to sanitize water. In Europe it is the most popular method of treating water. Ozone is one of the strongest oxidizers but it constantly has to be continually generated because it only has a residual of about 20 minutes. It is a good choice because it kills bacteria and oxidizes organics including chloramines, bather wastes and oils without changing the pH. Also it breaks down to oxygen which enhances the water by improving the taste and smell.

Because ozone has such a short residual time and limitations in how much can be introduced into the water other things need to be added to control algae. Ozone is therefore often used in conjunction with one of the halides such as chlorine or bromine.

Ozone can be made for pools and spas by 2 primary methods. In Europe the most common method is by Corona Discharge. Ozone is generated by using high-voltage electricity on pressurized and dried air. The ozone gas is then introduced into the bottom of the pool either directly or through the use of a separate chamber.

The second method of ozone generation is by using ultraviolet (UV) exposure of pressurized and dried air. The oxygen in the air is bombarded by the UV and produces ozone. UV does not have as great an output as can been generated by the Corona Discharge method but it is cheaper. I single UV light will generate about enough ozone to treat 10,000 gallons of water. This is why it is usually only found in spas and small home pools.

Ozone residuals are measured in parts per billion (ppb) using DPD as a reagent or by oxidation reduction potential (ORP) meters. If it is being used with chlorine or bromine any amount is effective. If you want numbers to go by then DPD readings should be between 0 and 100 ppb or a minimum 650 millivolts on the ORP meter.

Silver has been used to remove bacteria from pool or spa water by introducing silver through electrolysis or passing an electrical current through a silver electrode. It is not commonly used because of the expense of silver. There is also a danger of a black deposit forming on the walls if the water being treated is exposed to sunlight.

The final alternative sanitation is really still using chlorine, but it is not using “chemicals.”. Clorine generators are electrical devices that generate chlorine from salt dissolved directly in the pool water or by using a separate salt-solution (brine) chamber.

The brine type of generation is a similar method to how chlorine gas is produced commercially when it uses caustic soda to neutralize the pH. It can be designed for any size pool. A positive electrode in the brine tank generates chlorine gas which is directed into the pool or spa water for sanitation.

The other means of chlorine generation is through a generator placed in-line of the circulation system of the pool or spa. It uses an electrolytic cell that passes a current through electrodes in the flow of the low salt water of the pool and generates chlorine, caustic soda and hydrogen gas directly into the pool or spa water. By reversing the charge on the electrodes, scale build up is kept to a minimum. The caustic soda helps balance the pH. Because the products of the generation revert back to salt over time the process can continue all over again.

The generating system can be set to do a superchlorination so that chloramines are kept at a minimum. This method is very effective for spas and small pools and can save money because salt is much lower in price than chlorine chemicals.

No matter how you treat your pool and spa water to keep it safe test the water regularly to make sure that the sanitizer levels are sufficient to keep the “nasties” out.

August 24, 2017 at 3:02 pm
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