Downsides to salt pools

[chem geek]

Getting back to the original topic of this thread, which is what are the downsides to salt pools, I am curious if Australia, which has been using salt pools for about 30 years now, has modified their construction techniques or has had problems with corrosion, expecially in some of the older pools with SWG's. Also, I believe that many of the pools there use a much higher salt concentration than we do in the U.S.
I think that finding out this info would be most useful.

I agree with you. In the P.S. to this post I talk about a pool installer in Australia with whom I've had E-mail correspondence. This is what I wrote in that post:

I communicated with a pool installer from Australia who indicated that they see very little corrosion in their pools (SWG or non-SWG), but nearly all of their installations use the marine-grade 316 stainless steel, the paving is limestone or clay that is fired and that the supplier warrants for use in salt pools or it is coated to make it salt/sulfate resistant. They normally install heat pumps with titanium coils, rather than gas heaters (and such copper and cupro-nickel heaters do show corrosion). They also typically see higher TDS due to higher salt and sulfates in their tap water so even non-SWG pools have high salt levels, especially after seasons of chlorinating liquid usage.

Now since this is just one guy I talked with, this isn't a representative sample and it's based on his experience and opinion. It does seem that they take more care in selection of materials, but it also seems that they did this even before SWG pools were introduced due to their already very high salt (I'm guessing this is partly hardness, not just sodium chloride) and sulfates water.

If anyone else out there knows pool installers in Australia, it would be helpful to get some more information to confirm, counter, or expand upon what was said above. I did find this link to South Australian water quality and it appears that in the cities (metropolitan areas) the water hardness is around 100 ppm and the TDS (presumed to be mostly salt after accounting for hardness) is around 330 ppm. However, in the country, the water hardness is much higher with most in the 200-500 ppm range while TDS was also higher with most in the 350-900 range but with some over 2000 ppm. This link describes how "Australia's ancient weathered landscapes and some surface waters are naturally salty." There are other links as well, but generally they indicate a saltier environment (though I should point out, not at SWG levels).

[EDIT] It is also true that older SWG systems recommended salt levels of around 5000-6000 ppm, but most newer SWG systems are around 3000 ppm. So it would be reasonable to assume that since Australia had SWG pools earlier, that more of them (using the older SWG cells) would be at higher salt levels. That would make any potential corrosion issues worse so is another reason they would be more inclined to use more chlorine/sulfate/chloride resistant materials. [END-EDIT]

With everything said up to this point, I'm not too concerned with metal corrosion in SWG pools that use CYA (i.e. most outdoor pools). I think what we have learned that may not have been known before is that indoor pools using an SWG with no CYA risk corrosion of their stainless steel, even at "normal" FC levels of 3-5 ppm. The study Sean gave us and some of Brad's customer experiences also show that any pool where the chlorine is not monitored and goes sky high is also at risk and that this tends to happen more with indoor pools (probably because there is no sunlight to limit how high the chlorine level can get). As for hardscape materials, that still seems to be an open question but I'm leaning towards recommending more diligence in care of such materials in an SWG environment (either stronger materials or regular rinsing/diluting and/or sealing) though stone materials should really be cared for in any environment. The other open issue is sulfates in SWG pools and at this point I would recommend minimizing the use of non-chlorine shock and dry acid in such pools, but this is just being cautious and not yet born out by a lot of experience (except PatL34's caution referred to by waste in this thread).

Thanks,
Richard