What is the Safest Way to Purify Your Hot Tub or Pool?

by Pool Builders on 08-21-2006 in Articles

You are the proud owner of a swimming pool and/or a hot tub. Your big concern now, other than making sure no one drowns, is making sure no one gets sick or infected by using it.

You do that by putting something into the water to kill organisms that might be harmful to humans. The main options are chorine, bromine, Baquacil and ozone. You need to be aware that there are serious health concerns with the first two and, for pools at least, you can't use ozone by itself.


Chlorine has been around the longest, and is still the most common method of purifying the water. However, it is a poison. It kills things. That's what it is supposed to do. The problem is that it can be harmful to humans, although not as harmful as the things it kills, supposedly. The trick is to put enough in to kill the bad stuff, but not so much as to harm you and your loved ones.

Why can chlorine be harmful? For one thing, the body absorbs it. You can absorb as much chlorine in one hour of sitting in chlorinated water as you would drinking unfiltered, chlorinated tap water for a week! Furthermore, by-products are formed in the water when it comes in contact with organic matter, ammonia compounds and nitrogen compounds. The main source of those is people's bodies - the sweat, dead skin, urine, etc. These compounds reduce the effectiveness of the chlorine, necessitating adding more. They also cause the bad smell and burning eyes associated with pools. Some of the by-products have been linked to spontaneous abortions and other problems with embryos.


Bromine is also a poison but, for a number of reasons, might be a better choice over chlorine. Its high evaporation point makes it more stable, so it doesn't smell as bad or is as irritating to the eyes. On the other hand, that stability can make it more difficult to mix with the water and wash off your skin. It also may not be as effective against some bacteria as chlorine.


Baquacil is a form of hydrogen peroxide. It is more expensive than chlorine, but easier to use. It does not create health affecting byproducts like chlorine and it is also very straight forward to use, whereas chlorine can be a bit hit or miss.

There are, however, a couple of negatives to consider. It seems that after a few years, the water quality starts to decline. In addition, there have been reports of strange infestations occurring in pools on the Baquacil program. If this happens, you will probably have to drain the pool and start over again.


Ozone can be added to any of the above systems to make them more effective, cheaper to operate, and, in the case of chlorine and bromine, safer to use. Adding ozone allows you to reduce the use of the other chemicals.

Ozone is created in nature by lightening as it passes through the air, and by the action of ultraviolet rays on the oxygen in the air. That nice, clean scent you notice after a rainstorm is caused by ozone.

Ozone is a natural purifier and is the most powerful oxidizer that can be safely used. Its big problem is that it is highly unstable, so it does not last long in water. A hot tub has a relatively small amount of water in a confined area, and many people use ozone exclusively without health problems. For swimming pools, however, you will need to use other chemicals as well.

Making the Choice

Before you invest in a system to keep your swimming pool or hot tub safe for use, be sure to examine all the options carefully. Talk with others using systems similar to those you are considering. Do a lot of research and a cost/benefit analysis for each option.

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