tap water and distilled water for electrolysis my water electrolyzer which I've built using this pdf, produces less gas than I expected. In that file the author insists on using distilled water instead of tap water and I have used tap water. would it be the reason? 

Why is it so important to use distilled water since it has high resistance for electricity?
This article tells you to use distilled water because the salt in tap water will damage the booster. The author also tell you to add NaOH or KOH to the distilled water. Did you add these salts?