Quote Originally Posted by Reptoreef View Post
Well... look at it like this: lets say your water source has a TDS of 100-150 or so. You add an RO only and that drops the TDS to around 2 to 7.5(95 to 98% pure water)... that's a great range IMO. Now, lets say your water source has a TDS of 300 and you add the RO only and that drop your TDS down to around 6 to 15(still safe IMO, but border line). Above any levels 300, I strongly suggest the use of a DI resin following the RO process. I have a municipal water source of 250-300 and use RO and DI to filter my water.
What do I use to test my waters TDS?