Reverse Osmosis Water Filters
Reverse Osmosis Water Filters are generally considered to be the most effective form of water filtration available. The running costs are roughly the same as for the solid carbon/ceramic filters. RO systems are available either fitted to a single tap or plumbed into the main water inlet pipe, delivering filtered water throughout the house.
Pros: Highly effective filtration, running costs reasonable, whole-house systems available.
Cons: Initial cost, plumbing work required; all minerals are removed, so supplements are required to replace minerals with nutritional value.