Mineral sterilization vs salt water pool

[tropicdoc]

I met with a pool contractor who says he used to do saltwater pools but people were having rusting out of lights, pool furniture etc. He says he has put in about 500 mineral sterilization systems over the past 7 years and his clients are happy with it. Is at any good? He describes it as a low chlorine system with silky soft water that wont rust things.

[PoolDoc]

1. As far as we know, there is no such thing as "mineral sterilization". This sorts of claims are usually made for copper or copper + silver ion systems (added electrolytically or as copper & silver salts, such as copper sulfate), and they are usually made orally. If you can get such a claim in writing, we'd very, very much like to have a copy. EPA standards for sanitizer claims are set pretty high. Copper or copper + silver does kill algae, but it kills bacteria very, very slowly, and has pretty much no effect on viruses.

2. Salt systems (SWCG - salt water chlorine generators) are just a METHOD of adding chlorine to the pool, with both benefits and problems.

The added salt will accelerate corrosion of iron, steel or aluminum. As a result SWCGs are often not a good match for older existing pools.

Rusting or deterioration on DECKS is unlikely in wet areas. There have been problems in arid regions, where regular rainfall doesn't rinse of the pool water.

[chem geek]

See the table in this post that shows the relative kill times for chlorine vs. copper and silver ions. Basically, both copper and silver kill bacteria much more slowly than chlorine and they do not generally inactivate viruses nor protozoan oocysts. Copper alone does not kill fecal bacteria (it's best at preventing algae growth) so if metal ions are used both copper and silver should be used together to at least inhibit growth of most bacteria.

Note that these metal ions are not oxidizers so do nothing to get rid of the bather waste from your sweat and urine so you need to use an additional oxidizer for that. Also note that metal ions can stain plaster pool surfaces if their level gets too high or the pH gets too high and these levels are difficult to control.

You can read a lot more about the perils of using metal ions in the PoolSolutions article Swimming Pool Stains & Metal Ions: Copper, Silver, Iron & More.

Chlorine is both an effective disinfectant and a reasonable oxidizer and it is both inexpensive and easy to use. One just needs to be careful to not overuse stabilized chlorine products (e.g. Trichlor, Dichlor) because they increase Cyanuric Acid (CYA) that reduces chlorine's effectiveness.