According to their website it does require a cartridge filter, but even with that one attached I would not trust it. It can be used, there is no harm in it, better than nothing. Personally I have filter system installed under the sink and use it for domestic purpose, also fill the water tank when needs.
I fixed lots off coffees machines equipped with water systems, but none of them could stop 100% the limescale. The coffee boiler and steam boiler always are the victim of it.
To keep the machine clean, use that cartridge filter provided, descale the machine regularly, I use second stage of water filter (now my water system needs service, I ll do it myself), instead, I use water from Brita water filter.
One more thing is to remove the brewing unit, clean it up and use silicone grease for brewing sealing and around the piston area, each fortnight. If all these are not working call me
This is the cartridge filter:
Interesting post about machine maintenance. I use a brita jug to filter the water i put in my machine and descale it when the descale light comes on the machine. I also use the silicone grease as in this video.
What do you mean by lubricating the piston area? Is there a youtube video showing what to do?