Finally bought my rodi!

The probes on the dual inline TDS meter are placed after the RO membrane (IN) and after the DI filter (OUT) so you are reading RO only and final RO/DI. There is little you can do with the tap water TDS other than send it through the RO so that reading is not as beneficial. I have two of the dual inlines on my MaxCap UHE so I read the tap water after it has been through the preilter and carbon block (IN) post RO (OUT), post MaxCap DI (IN) and post SilicaBuster DI (OUT). Even though I have all those I like using my handheld too.

 

Aaaah your right.. I guess I should have looked alittle closer at the T fitting for the sensor... thanks AZ.

Makes sense now. Although I am curious what my taps tds is to see what I've been drinking all these years.

 

I also have a handheld, the HM TDS-3 per AZ's advice, I love it. It's very accurate, easy to use and not expensive. Even though I also have the dual in-line meters on my SpectraPure, I like using the handheld for all my testing. My in-line meters would read around 1-2 in and 0 out always.

Here's a link to the handheld in case:
TDS-3 Handheld Meter With Carrying Case - HM Digital

It's readily available on eBay for $22.20 shipped from a few different sellers, worth it IMO: HM Digital TDS-3 Meter, Hydropo Water ppm Tester, TDS3 - eBay (item 370281460154 end time May-25-10 18:45:40 PDT)