Not pissing at all could indicate you are a ghost. Check by taking a selfie and posting it online, if you see a red circle around you, you are in fact a ghost.
I chatted to someone on the train once who told me she got addicted to the habit of drinking water and was hospitalized for a month or so because she basically flushed out all of her electrolytes and was deficient in everything. She said she was at 5-6L though.
I probably average a little better than that. I also drink tap water and am fortunate enough to live somewhere with excellent water. I have heard of people having similar issues with distilled water.