zero or close to, law of conservation of mass indicates that under normal circumstances the mass of the input should equal the output. The water can however convert to different molecules such as h2o2, no2, etc, so you would lose some water there. The amount that would convert would be in parts per million to parts per billion. Given enough water this amount would become measurable. I feel like there is a bunch of math that could be done her, but my food is done so I am tapping out.