XT-3 is certainly formulated regarding usage of tap water. Meanwhile probably thousands of customers are using it with tap water, and without problems. My results with tap water have also been without problems.
That one customer had problems with a certain type of demineralized water (who knows whether the process were done properly at that facility) does not make the product a bad product.
At the end, the problem was solved. That is what counts.
I do agree about the water item, but I can't accept that the problem could be XT-3.
It is strange that the quality of one demineralised water producer can cause that kind op problem: a pre-packed powder developer not to solve properly.
It is rather strange too that distilled water, and not tap- nor demineralised water, must be used by OP to mix XT-3.
Knowing that XT-3 is particularly formulated to solve fast, safely and thoroughly in tap water.
To my personal opinion, the problem isn't fully solved, although not in the environmental way: shouldn't tap water be clean, pure, healthy and 'safe to be drunk'?