Salt is pool-grade (no additives)? CHECK!

Fill water? Jury still out....

As for bucket tests, those really won't work so well in my case. I have high CH from being in the Southwest (CH ~ 500ppm), so the only thing that would scale out in a bucket for me is huge amounts of calcium. But that does bring to mind another problem which may not be a big deal for your vinyl pool - sequestrant interference. It is well published on the Taylor website and in other forums that the calcium hardness test, which uses EDTA drop-wise to chelate the calcium ions and cause the indicator dye to change colors can be interfered with by the presence of a sequestrant in the water. Now this all depends highly on the chemical affinity of the sequestrant you use versus EDTA for the Ca ions but it is possible to slow down or arrest the color change of the CH indicator dye. SO it makes me wonder in high CH pools if Jack's Magic goop (HEDP mostly) would even work all that well considering the sequestrant will go after the Ca ions just as easily as any metal ions.

What's your calcium hardness? I know you operate a vinyl pool and probably don't test for it very often, so an old number is OK.

As for Jack's Pink versus Purple, etc...if it's all HEDP and just different concentrations in the bottle, then I don't see why it would matter at all if you have a salt water pool or not. I think I read somewhere on here once that it is indeed just marketing, so you can probably ignore it and just buy the color of Jack's Magic potion that works best for your water.

I think someday I'd like to modify an exercise bike to run a small water pump and then hook an inline filter up with those Culator bags and use the energy produced by my much needed workout sessions to help filter my pool water....beats paying the electric company I suppose