I can't.

I have a vinyl liner but no heater.

Based on all the discussion from last year (which were lost ) and the fact that SWG sellers don't warn against using with a vinyl liner, I feel pretty comfortable. I can't see why the ppm of salt we're talking about would degrade vinyl. I bet Gatoraide has a higher salt content and it comes in plastic bottles

I added another 40# bag this afternoon. Might get a chance to swim late tonight.