Originally Posted by homealone

Hard to say, if you are prone to hypertension it is one source of sodium that can be avoided.

As far as I can tell there are two 'main' types. Ones that just have an active carbon filter & possibly silver particles are designed to remove particulate matter, reduce the number of bacteria & neutralise any nasty tastes or odours.

The second type have the same as the above, but have an ion exchange resin, for removing 'hardness', as well - which it does by swapping the calcium ions in the hard water, for sodium ions, which don't deposit as limescale, like the calcium ones do.

Incidentally, it is worth checking the sodium content of bottled water, especially 'mineral' water, as that can have high sodium compared to tap water

(can you tell I have high blood pressure )