This is the one I have had for the last 8-10 years with no problems. We are very happy with it and put one in our second home about 3 years ago.
http://www.ecowater.com/EROR350.php
I get replacement filters here:
http://www.purewater4u.com/store/ecowater335.shtml
Mine says to replace prefilter and postfilter cartridges at 6mths to 1 yr and the RO cartridge between 18 and 36 months. I let mine go for about twice as long as recommended and the water still tests/tastes good.
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74 Targa 3.0, 89 Carrera, 04 Cayenne Turbo
http://www.pelicanparts.com/gallery/fintstone/
"The problem with socialism is that you eventually run out of other people's money"
Some are born free. Some have freedom thrust upon them. Others simply surrender