SWG w/ Hi TDS?

[chem geek]

Not only for considering an SWG, but in general TDS itself doesn't matter. What matters is what the TDS is composed of. You already pointed out the single biggest problem for an SWG (in terms of scaling) and that would be a high hardness level, though specifically it is the Calcium Hardness (CH) that is the relevant number. The other very important factor is Total Alkalinity (TA) and pH though the latter is the most easily adjusted.

So I wouldn't worry about the TDS, but get a complete set of test numbers: pH, Total Alkalinity (TA), Cyanuric Acid (CYA), Calcium Hardness (CH) ideally using a Taylor K-2006 test kit that you have or purchase. My guess is that with Total Hardness at 900 ppm the CH will be somewhere around 550, but this can vary a lot in different waters so testing is really required. Even if the CH level is on the high side, you will probably be able to mitigate that by having a lower TA which is something you'd want in an SWG pool anyway.

So, let's see those numbers!

Richard