[karsseboom]

Originally Posted by bertoni

your filter is not working. The output from the ro phase should be more like 3 ppm, assuming the meter is correct. I'd calibrate the meter or get a second opinion to be sure, and then work on the filter. The membrane might not be seated properly, for example. To be sure, you should produce about a gallon, at least, of ro water, and throw away the first half gallon. The membranes often leak while sitting idle. You could try the water after the di phase, too, but i think that the cartridge is shot.

Distilled water isn't necessarily 0 tds, for a number of reasons. In addition to contaminants from the coils and after the fact, carbon dioxide can raise the tds, and distilling will leave some other contaminants in the water as well.

i tested about 25 gal of distilled water from different source and they all read zero...