While poorly treated pool or spa water can potentially kill bathers (or even people nearby and not in the water) fortunately this is fairly rare. Illnesses that confine you to your bathroom for a week wishing you were dead, or even worse in the hospital ICU for a spreading infection however, are more common. Most people do not eat chicken that has been in the fridge for five days because you can get sick. The reality is that most of the time you would not actually get sick…but you could. Swimming pool and hot tub water is the same thing. If you do not bother to balance your pool and spa chemicals then you are just eating five day old chicken hoping for the best.
Of all the chemicals that get used in swimming pools and hot tubs, the ones that are there to prevent bacteria growth and kill any potentially dangerous pathogens in the water are called chemical sanitizers. The most common of these chemical sanitizers are chlorine and bromine. When used correctly in a body of water they will completely prevent bacteria, viruses and pathogens from living, growing and multiplying. The only catch is they are not great for people and only in very small doses is it considered acceptable. This is why you do not simply add a wholesale amount of liquid chlorine to your pool once per year. The levels need to be monitored and maintained. There are also a small handfull of situations which can develop in the water where the chlorine that you use is unable to work properly such as when you have high CYA levels (stabilizer) or if your pH gets above 8.0 where chlorine is almost completely not effective.
There are a host of “alternatives to chlorine” in that there are options that do some of the things that chlorine can do to protect your water. It is important to understand that even new technology systems like hydroxyl radical based AOP systems or reliable older technology like germicidal UV lights still lack the ability to do everything that chlorine can do. The same can be said for every other system on the market that does not use chemicals sanitizers like chlorine in that they probably work to help the water, but not as effectively as chlorine and the four layers of protection it provides.
