Topic Split off from this Thread.
First I want to say that this board is very interesting and helpful, and I don't mean to start off my stay here by disagreeing, but....
It is true that sunlight can cause the production of ozone, but in such miniscule amounts that it has no real world effect in a pool. It is also true that most ozone generators for residential pools do next to nothing. Particularly here in Houston where the humidity is high, many appear to do little more than produce nitric acid, and you won't see any reduction in the need for chemicals. In fact, by relying on these systems for their "magic" effect on chemical use, you often end up with a worse situation than with no ozone at all.
That being said, ozone systems are being used successfully in residential and commercial pools (as well as in water and waste treatment) around the world as well as in the US as primary sanitizers with all of the good effects advertised, but these are well engineered, well laid out systems that tend to be expensive. My own set up uses an oxygen concentrator, drier, 120 gallon holding tank and an in floor system to push ozonated water through the floor heads 24 hours a day (I use a dedicated variable speed pump at low speed for most of the day and kick it up to a higher speed an hour before people tend to use the pool and at an even higher speed during pool use....and highest when the whole neighborhood is over). Of course, slow speed means even more time in the contact tank so more complete oxidation, etc.... I also maintain a residual amount of cholorine of .2ppm which given the size and output of my ozone system may be unnecessary but this is Houston with all of its nasty attendant pool problems, so for now I'm most comfortable going this way. It also means I have chlorine in the water should the power go out. I believe that because of my ozone system, TDS remains very low, PH is stable and ORP is high and I have incredibly clean, sparkling water. Haven't experienced algae problems and no amount of bather load appears to get my chemistry out of whack. I'm not enough of a chemist to say that ozone does or does not destroy chlorine, but in my system the primary ozone action is in the holding tank, and chlorine is introduced way downstream just before the water enters the pool. I do know that ozone eats up chloramines produced by chlorine's interaction with organics, but the ozone itself also oxidizes the organics very well itself, leaving very little if anything for the chlorine to turn nasty with.
I think it is easy to dismiss ozone because here in the US on the residential side, there has been so much snake oil sold that the indifferent to bad reputation is mostly well deserved. And not everyone will want to invest enough to make it work right. As many of you suggest, with constant attention and a little bit of smarts (and good pool education!) you can get some if not many of the same results at perhaps a lower price (although my chemical costs are waaaay low put up against a very small increase in my electric bill), so I guess it is a matter of preference. Just didn't want to see ozone dismissed entirely as a very good option. Instead, I will save my incredulity for those fish pond/algae pools. Yuck.
SWG certainly have their advantages in terms of ease of use, but salt in the pool (and chlorine itself) has its drawbacks as well. Careful research is required to figure out what fits your situation!