This is close to what I would expect, based on some back-of-the-envelope calculations I made last night (Hey, we all can't be like ChemGeek taking things out to 34 significant figures!). Since the salt content in SWG pool is only twice that of a bleach pool, should we expect the water from an SWG pool to be practically any worse on decking and natural rocks than the water from a bleach pool? I've been trying to find an answer on this one for a few months.Most true SWG pools are in the 3,000 ppm range or so. Over time, a bleach pool will average out around 1,500 or so. Some folks are more sensitive to salt levels than others.
Since the problem is with salt recrystallization pressure, the effect is non-linear (it's more like a threshold) so the factor of two difference in salt levels can be significant. On the other hand, with enough splash-out and evaporation even non-SWG pools with 1000 ppm or 1500 ppm could create a problem. Nevertheless with an SWG pool 2-3x more concentrated in salt, at a minimum any degradation would be 2-3x faster. If the rate of salt removal in cracks from summer rain vs. introduction from pool water were near balance in between non-SWG and SWG salt levels, then you could see the non-SWG not produce any significant degradation while the SWG produced significant degradation. If you get a lot of summer rain, then even the SWG salt levels would not be a problem since they would get washed-out/diluted at least as fast as splash-out built up the level.Since the salt content in SWG pool is only twice that of a bleach pool, should we expect the water from an SWG pool to be practically any worse on decking and natural rocks than the water from a bleach pool?
Thanks, Chem Geek.So there are many factors that come together where the salt level in the pool is just one of them. Other factors are the rate of splash-out, the rate of evaporation (dependent on temperature and humidity), the rate of dilution (say from summer rains), the type of stone (soft stone is worse).