I've got the "under the sink" double filter system from Pozzani (option 1, the scum and limescale add-on, as well as the chlorine/sediment/heavy metals filter) plumbed in, and tee-ed off to feed a drinking water tap and also provide a filtered/descaled water supply to my Coffee Machine... works great, and I find that I actually drink far more water now, purely because it actually doesn't taste awful... (According to a friend who works for the water utilitys we're on a Aquifer fed supply in the surrounding villages , and with all the coal-measures around here, apparently the water needs a fair degree of treatment to be potable...) The limescale filtration certainly works as well - before fitting it, the kettle used to scale up in a matter of months, the coffee machine needed descaling weekly... now, the kettle gets a treatment once a year if that, and the coffee machine, once a month whether it needs it or not...