Hi - I have a SWG and have a stacked flagstone weeping wall, as well as a stacked flagstone spa spillover and neither have shown any signs of erosion, corrosion, or pitting despite water running continuously over these things 6 hours each day. I've had the pool since August of 2006.

I have done quite a bit of research on this topic, and much of what's out there is very anecdotal, even the stories written about in the link that kurtv provided. However, given my research and personal experience with these things, this is what I know:

- many people forget that chlorine is just as much a corrosive as salt is! In fact, what makes salt (NaCl from High School Chemistry) corrosive is the Cl (Chlorine) part of the molecule.

- many SWG owners are under the impression that having a SWG means no longer having to watch their water. I hear so many SWG owners say that their pool is so great and worry-free that all they have to do is dump a bag of salt in once or twice a season! If you don't watch your water, it could turn into a really corrosive agent!

- another thing to watch out for - stabilizer (CYA or cyanuric acid) levels. Stabilizer is required in outdoor chlorine (yes, salt pools ARE chlorine pools as well) pools because it helps reduce the breakdown of chlorine via the sun's UV rays. But more importantly, one side-effect of not having enough stabilizer is that it magnifies the corrosive effects of chlorine! For example, with little or no stabilizer, chlorine at normal levels (4-5 ppm) actually becomes a 30x STRONGER disinfectant AND oxidizer! Now guess where the corrosion comes from?

Having said all this, my conclusion? Enjoy your SWG, but PLEASE watch your water! Having a SWG doesn't mean you don't have to watch your water, but in fact the opposite. I test my Cl and pH levels every 2 days, and test TA, CH, and CYA levels weekly. I know people who take their water to Leslie's for testing only every month or so!