meter is not an inline unit I take it since you tested your tap water with it. When you test your TDS
make sure the vessle your using to hold the test water is absolutly clean. Just a few dust particles can screw up your TDS
measurements. Also make sure you use seperate vessles for tap and RO
water testing or you wipe and dry the vessle upside down before testing the RO
. The reason is that RO
is so close to pure H20 that even the most minute contaminates can give a false TDS
I would be willing to bet if you measured your RO
a half dozen times over the corse of an hour you might end up with 4 different readings all within 3-5 points of eachother. At the low level your testing that can be a fairly significant percentage of error but at the dirty tap water side a 3-5 diffierance is insignificant.
I would say acceptable RO TDS
measurements would be 10 or under. Yes adding an DI
stage should bring taht down to 0-3.