I read the other day that distilled is best but I can't remember the reasoning. It was a fairly in-depth thread and I was actually looking for info on nic base so I didn't read the whole thing. I have some diluted VG, it uses distilled at 10%.
Thanks for that, I was still a bit confused even after reading it but dug a bit deeper, different section and it appears that neither distilled or de-ionised water is safe however on the advice of a chemist it is "PURIFIED WATER" we should use to mix with VG. Just purchased some DE IONISED WATER AS WELL. Sink I think. PURIFIED WATER is in fact distilled water produced in lab conditions and shipped in sterile containers, and is used in medical facilities.