Saturation Index

[DONNIE]

So I don't need to include TDS in the saturation index or do I use my 3600 ppm salt?

[chem geek]

So I don't need to include TDS in the saturation index or do I use my 3600 ppm salt?

You should include it in the index, using say 3800 ppm (200 ppm more than the salt measurement), but don't bother measuring TDS explicitly.