The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.
I have the same filter mine reads 0, sometimes but most time the in reads any where from 300-,2 so it just depends I guess I got city water and went to them to get a read out and they claim 250 tds is most they put out so mine seems acurate
Where do you have the "in" connected to? After the DI is where the "out" should be and it should read 0ppm. If the "in" line is before the DI and after RO it is possible for both to read 0. You can change your "in" to before you RO filters directly from house supply and you will get some reading on your tap water. That is beat way to test tds meter.
I think your tds is fine then. Your probably have low tds on your tap water so your RO is 0 as well as your DI. Like I said you can move the "in" to your tap water before your RO filters to find out what tds of tap is. The RO filters will take out about 90% of tap water tds.
You said you saw reading of 26ppm I think it was. That could be "tds creep". Sometimes when first start your RO system could have build up of tds that is released. When I first turn on my system I let the water run down the drain until tds goes up that comes back down before I start making tank water.