The Y-3 implant is supposed to remove radiation from all drinks ingested.

It does this fine when drinking dirty water from a bottle, or nuka cola, etc.

However, it doesn't work at all when drinking water from water fountains - you still get the rads.

I'm not refuting this being a bug, but I can see why it is so.

To make the implant work on water fountains, they would have had to gone in and replaced every instance of a fountain in the game. That is impractical to do. So in the end, its one of those bugs that will never get fixed.