100% agree with the TDS meter. The answer to the question is that it depends. The cost of adding a DI is not that much and with a TDS meter, there is no guessing game =, including knowing when to change the filters.
I did a write up on my portable RODI I got 5 years ago knowing nothing. I was about to upgrade to one of the highly recommended BRS units in the $150 range, but got a TDS meter for $20 first.
Low and behold, 5 years later and a full year since I replaced my filters, my $99 (today's pricing) RODI was at 0 TDS ( and only 2 TDS between the RO and DI). I make between 5 and 10 gals of RODI a week. My unit is the 75 GPD.
Totally changed my thoughts on the unit. Why spend $50 more when the TDS is giving me proof the $99 unit as good if not better than a more expensive unit.
As for chlorine v chloramine, sellers will tell you that if your water supply uses chloramine, that you need a special filter, this has been debunked. If you do have chloramine, and use the standard filters, use an inexpensive chlorine test (pool and pond type) to test your RODI water. If it's present you can treat the water (basic aquarium water conditioner) until you change the filters an upgrade to a chloramine one (but odds are the basic RODI will remove the chloramines).
Here is my review of my $99 portable Reverse Osmosis Revolution RODI unit:
I purchased the 75gpd Reverse Osmosis 4 stage Aquarium RODI unit 4 or 5 years ago. It's portable so originally I used to hook it up to my kitchen sink, but my cheap faucet couldn't handle the pressure after a while, so I moved it to the basement, removed the kitchen facet adapter that came...
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