It always amazes me that the most important bit of advice concerning buying a RO / DI unit seems to always get left out amongst all the opinionating and infighting.
And that is, to have your tap water supply tested for TDS level before you buy a unit. You can, of course, buy your own handheld TDS meter and do this yourself - or you can have someone do this for you (most decent LFS will test a sample of your water for no charge).
Then base your purification decision at least in part by your starting point.
In my case, my tap TDS runs 205 - 225 ppm depending on season, temp, etc. In my case , I bought an Ebay unit for home use. I added a dual inline TDS meter, and rerouted the DI canister from a horizontal position to vertical position. Other than that, no changes or modifications... I have made over 800 gal of *0 ppm* water so far, and have changed my prefilters once. I changed them because I read somewhere (here on RC, I thought) that it is a good idea to change them every 6 months, regardless of "what they look like" or what your TDS meter reads. In hindsight, perhaps I was too hasty. I certainly didn't change them out because of performance issues. And the supposedly "shoddy" RO membrane that came with the unit is giving me, In my case, an output of 6 - 7 ppm (RO only) on that 205 - 225 ppm input... well, that's about a 97% rejection rate... !
Anyway, my point is that knowing my TDS level beforehand allowed me to go with a lower cost, (perhaps) lesser quality unit without sacrificing the desired result (which is 0 TDS water).
Now, for anyone to come on here suggesting that in ALL cases an Ebay unit "will work" is just plain wrong. But to say that in ALL cases they "don't work" is wrong, too. It really depends heavily on what you need your system to do, and where you are starting from in terms of water quality. I remember a fellow posting several months back (from Seattle, I think) that he had tap water with <50 ppm TDS - from the tap -and he was told an eBay unit WOULD NOT give him 0 TDS water.
?????
And, for the record, let me say clearly that had my initial tests showed a TDS anywhere near the 1000 ppm that AZ Rat has to deal with, then OF COURSE I would need a "premium" unit!
Oh, and I too know a little about water quality. As a Pharm Engineer, I helped design and install a system at my Companies newest Stage II DEA / FDA Compliant Manufacturing Facility (CMF). We use a system called a Milli - Q that has a 400 gpd capacity and retails at over $18,000 (not including filters)...
Now that's what I call a "premium system" :lol:
