Save your money if you plan on buying a small charcoal filter for your sink. The water runs through it too fast for it to be effective.
As for drinking water, that's a hotly debated topic. I have used Distilled, and RO, in the past, but currently drink Natural Spring Water with TDS of around 200 ppm.
There's strong evidence that Man shouldn't drink water at all, getting all the water needed in his Natural food (juicy Fruits and Vegetables). But when you're on a Water Fast, an exception can be made.....WY