I just posted the following in another thread but I think it bears repeating here!
I suggest you look through the forum. You will find some answers there. Chlorine is the safest santizier for an outdoor pool. Copper/silver/zinc ionizer systems (including ecosmarte) are NOT primary sanitizers, no matter what the marketing hype surrounding them says.
Ozone and UV are not primary sanitizers either.
IMHO, a salt system is the way to go. It is a chlorine system but it greatly simplifies pool maintenance.
Here is something that I posted in another thread but I think it bears repeating!
There are only 3 EPA approved sanitzers--chlorine, bromine, and biguanide (Baqua, SoftSwim, Revacil, etc.) ALL OTHER sytems are supplimental and MUST be used with a residual sanitizer (usually chlorine or bromine).
As far as biguanide, it has more drawbacks than advantages and most people that use it end up converting to chlorine after a few years once the pink slime and white water mold takes hold. It can also attack and destroy certain plastics and at least one major spa manufacuter is now telling it's customers not to use it for this reason.
Bromine has no advantages for an outdoor pool since it cannot be stabilized againt UV light like chlorine can. It is also a known sensitizer and many people develop an allergic reaction to it. It does have some usefulness in indoor pools and in spas that do not receive sunlight.
That leaves chlorine, which is the best choice for an outdoor pool.
There are supplimental systems that claim they can reduce the amount of residual chlorine in the water. Most are metal based (copper, silver, and zinc). However, the low residual chlorine levels (usually .5 ppm) are NOT enough to insure that the water is sanitized. They will prevent algae growth but the kill times fo metals are very slow and a minimum 2 ppm free chlorine should really be used with these systems, IMHO. One of the biggest drawbacks to these systems is staining of pools and people (copper is what causes green hair). Many of them need to be run at a much lower pH than is commonly used to help prevent the staining but this can be aggresive to the plaster finish of a pool.
Ozone and UV light provide NO residual sanitation and must be used with a residual santizer. Ozone and chlorine tend to destroy each other so chlorine usage is usually higher in a system that also uses ozone. Ozone tends to work better with bromine but does cause bromates to form in the water. Bromates are a suspected carcinogen in drinking water.
There are some companies that make some very dubious claims about their products that just don't stand up under scientific scrutiny such as breaking water apart into 'radicals', etc. This is pure snake oil!
EDIT: Ecosmarte is a prime example. Check out this website and read the second box under "Other electrolytic processes, completely off-the-wall" where they talk about Ecosmarte and debunk some of the pseudoscience claims that they make!
http://www.chem1.com/CQ/aquacrack.html
Intersting read!
Getting back to metals--they are often marketed as 'mineral' systems. If you consider copper sulfate and silver nitrate minerals then perhaps they are. Minerals sound more spa like and healtly than metals, don't they? It is interesting that in Canada these systems can only be registered as algaecides and not as sanitizers and in Australia they are required to be used with normal and not reduced sanitizer levels to provide quick kill times and proper sanitation. If only our own EPA was so dilligent at protecting our welfare (but that's a whole other can of worms, isn't it?)
There is a lot of negative press about chlorine but much of it has to do with chlorine used to santize drinking water. Some of it IS applicable to chlorine in INDOOR pools since some of the disinfection byproducts such as the TMHs do collect in the air but this is not really a problem for OUTDOOR pools since UV light breaks them down and they cannot concentrate in the air as they do in an enclosed indoor pool.
Hydrogen Peroxide, Potassium Monopersulfate and Sodium Percarbonate are oxidizers and NOT sanitizers and will not keep the water sanitized by themselves. They are usefule when used in conjucntion with one of the three EPA approved sanitizers as an oxidizer but they do present their own sets of problems.
Where does this leave us---with chlorine!
I am curious why you are looking for a low chlorine system. If you have a true chlorine allergy then biguanide is your only real alternative and you will have to live with it's shortcomings.
Chorine is actually the safest and easiest santizer to use in an outdoor pool. If you have an indoor pool it does present a few problems but they can be overcome (such as using potassium monopersulfate as an oxidizer instead of 'shocking' with chlorine) or bromine is also a viable alternative.
