tds readings ??

Bought a new unit from bulk reef and the tds reads 0 out but only 7-9 going in. First one I have used but something is not right.

 

If you are referring to a dual inline TDS meter then it is correct as far as the accuracy allows anyway. Inlines are normally installed with the IN probe on the RO treated line and the OUT probe after the DI. The problem is to troubleshoot a RO/DI system you need a minimum of 3 TDS readings. Tap water TDS, RO only TDS and RO/DI or final effluent TDS, the inline only has two and cannot be used portable.

Get yourself a good handheld TDS meter like the HM Digital TDS-3, TDS-4TM or AP-1 and forget all about the inline which is not nearly as accurate anyway since it lack ATC temperature compensation and can be significantly off. To measure your RO rejection rate or removal efficiency you need to know the tap TDS and the RO TDS. Since the RO does 90-98% of the work this is critical.

 

Didn't look at it that close but makes sense thanks