I know some say not to use it. But a very seasoned gardener talked me into trying it few years ago. And after running a few side by sides, r/o vs tap vs distilled, I stuck with distilled. Consistant 7-10 day rooting time for clones, a few days less than the others. And for soaking my peat pellets for germing seeds germ rates really didnt increase, was getting close to a 100% anyways. But the speed at which they rooted once germ did increase. My friends 'logic behind it is this. Distilled water is so sterile it offers the plant nothing but moisture, forcing it to expedite the rooting process in order to feed. But only the first few days of rooting then on to your normal water source.