The internal system we have is "reverse osmosis" and it cost around 550 euros to have fitted, which was a couple of years ago. The best thing about it is that the water is very safe to drink so more buying water in the shops! As regards annual servicing of the main unit, from what I can gather, there is no need for that to be done, but, again, it may depend on the particular system that you have. In any event, I don't imagine that another month or two without a service is going to have any harmful effect so that you can get more feedback before waving good-bye to 130 euros...