How much is the TDS increased if Borax is added to 50 ppm

[chem geek]

You shouldn't need to worry about TDS. When you add 50 ppm Borates (via Borax) to your pool AND add enough Muriatic Acid to restore the pH, the TDS increases by about 417, but much of this increase is with neutral Boric Acid, B(OH)3, so only an increase of about [EDIT] 139 [END-EDIT] will register on a conductivity meter (mostly as sodium from the Borax and chloride from the acid you need to add to lower the pH since the Borax raises it). So, the added TDS is just salt and Boric Acid, which is nothing to worry about.

If you are using the spreadsheet to calculate CSI and other parameters, you'll notice that the increased TDS barely nudges the index so is nothing to worry about.

Richard