proofing water improvements

[JohnJacob]

We are interested in hearing the forum's thoughts on improving the quality of their proof down water. We have been using a slow proof down method which I believe has improved our spirits, but I want to go further. What can be done to improve local water if you don't happen to be lucky enough to be in a limestone heavy part of the country? 

I am currently experimenting with the following:

1. Switching to municipal H2O instead of RO water. 

2. Adding a re-mineralizing filter to the RO set up.

3. Experimenting with adding various levels of salt/ minerals to the proof-down water to improve whiskey finish. 

Thoughts?

[Silk City Distillers]

The last part is interesting, but raises interesting compliance questions.  If you are adding NaCl - sodium chloride to your water - then using that water to proof the whiskey - is that considered an additive to the whiskey - requiring formula and approval?  At what point does it become coloring/flavoring/blending material?  Taking it to absurdity - is it now salt-flavored whiskey?

Generally, I would imagine the TTB is good with subtractive processing on water (filtration, carbon, deionization, reverse osmosis) - but would they similarly accept additive processes?  For example, dosing a wide array of chemicals?

[JohnJacob]

48 minutes ago, Silk City Distillers said:

Generally, I would imagine the TTB is good with subtractive processing on water (filtration, carbon, deionization, reverse osmosis) - but would they similarly accept additive processes?  For example, dosing a wide array of chemicals?

I would be interested to hear the TTBs thoughts as well. I would guess that it's been taken with them in the past.