TDS meter Readings?

[Pimpin Chirp]

So I recently purchased a TDS meter to check the readings off of my RO/DI unit and the reading is 003 verses my tap water which is like 400plus...So i was wondering what levels should my readings be at and what readings are too high so I'll know to replace my filters

[TheBeak]

the prefilters dont affect TDS much if at all, only the membrane. change the membrane if you see TDS over 25. not gospel number, but good ball park.

change prefilters as often as you can afford.

[OneDummHikk]

If your after-DI readings are above 0, then the DI cartridge isn't doing its job. You should read 0 with a properly operating RO/DI unit.