Ebay RODI?
- Thread starter nikonosis
- Start date
Probably because a lot of the units sold on eBay are horrible. That is the risk you run buying from an unknown source. You may get a gem, or a lump of coal. The best approach IMO is to find a good quality unit through research and then see if you can find on for cheap (eBay or otherwise). I got mine of eBay as well about four years ago and it worked like a champ, but then again maybe we just both got lucky. 
Fishbulb2
New member
Just do a search for "EBAY and RO/DI". It's been argued by AZdesertrat, Bean, and others to death. Probably the biggest point is the crappy membranes. Most units will put out a very low perfectly acceptable TDS. But the question is, how are you getting that? Is the membrane or DI resin doing all the work. If your membrane doesn't have the highest rejection rate possible, then you are either spending much more money on DI resin or just ignoring the issue and using depleted resin.
I'm curious, what is the actual rejection rate of your membrane? Do you know it?
FB
I'm curious, what is the actual rejection rate of your membrane? Do you know it?
FB
nikonosis
New member
Nope I don't know but I do know that my DI resin is in a clear tube and it changes color when it goes bad. I have only changed it once in a years time... Also, if I wanted when I change out my membrane I can just buy a filmtec dow 75gpd membrane and then I will have the best membrane made. So really does it make a diff?
Only $37 shipped...
http://cgi.ebay.com/Dow-Filmtec-Rev...ryZ20684QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
Fishbulb2
New member
Yeah, the color indication is poor. Your DI resin is probably cached long ago. Without a TDS meter, this really isn'y even a conversation worth having. Not to sound rude but it reduces it to shear opinions and "well i'm happy with it" type arguments. I've had two ebay membranes on my last unit. Both got 94% rejection. My new filmtec gets 98%. So my guess is my operating cost 3X lower than yours. but we won't know unless you get a TDS meter.
FB
FB
Fishbulb2
New member
Yeah, the color indication is poor. Your DI resin is probably cached long ago. Without a TDS meter, this really isn't even a conversation worth having. Not to sound rude but it reduces it to shear opinions and "well i'm happy with it" type arguments. I've had two ebay membranes on my last unit. Both got 94% rejection. My new filmtec gets 98%. So my guess is my operating cost 3X lower than yours. but we won't know unless you get a TDS meter.
FB
FB
You can measure the effectiveness of your RO stage(s) by bypassing the DI and measuring the TDS. My old RO unit (no DI) put out 17ppm TDS water from 471ppm source water the last time I measured it. I felt for 80 bucks, that 96 percent rejection was pretty good.
nikonosis
New member
Did I ever say I can't? I just don't feel like getting up and unhooking a few lines, measuring it, and then doing some math for you... Can you tell me what the difference is between a $250 rodi that use a 75gpd filmtec dow and a $75 unit that use a 75gpd filmtec dow?
btw how am I getting 1 TDS with a burnt up DI, like you say I have?
Fishbulb2
New member
IMO gettting 1 TDS by using crappy components and then dumping DI resin at it is worse then getting 1 tds by using high quality membranes and prefilter and then using hardly any resin to get there. But I wouldn't know. I haven't had 1 tds since I got real DI canisters. Now I only get zero. Also, DI resin works purely on affinity. So lower affinity ions, like phosphates and nitrates, will be replaced by higher affinity ions like chloride in your resin. So nitrates and phosphates are more likely what's making it through your resin.
It also depends on what your input TDS is. The effects of the EBAY units is of course magnified with lower quality tap water. If you have very low TDS input water, then you will probably be just fine and it won't matter much. If you TDS is high, then it's just not possible you are only using 6-16 oz of DI resin a year with a low quality membrane and still getting 1 tds output.
The idea of "1 TDS = 1 TDS is good enough for me" is like comparing a horse and carriage to the car as means of transportation. yeah they might both get you there but there's still a difference.
FB
It also depends on what your input TDS is. The effects of the EBAY units is of course magnified with lower quality tap water. If you have very low TDS input water, then you will probably be just fine and it won't matter much. If you TDS is high, then it's just not possible you are only using 6-16 oz of DI resin a year with a low quality membrane and still getting 1 tds output.
The idea of "1 TDS = 1 TDS is good enough for me" is like comparing a horse and carriage to the car as means of transportation. yeah they might both get you there but there's still a difference.
FB
Fishbulb2
New member
17 TDS is very high to run to your DI. With a 98% rejection membrane you would spend 1/2 the money you currently do on DI. Lots of Filmtec membranes will get even higher. Also high quality units from reputable sources do not have to cost $250. You guys are only looking at the spectrapure unit. There are other high quality cheaper options. The cost differential will close very quickly with a higher rejection rate. Although 96% is impressive for a 100GPD membrane. I'm curious as to what these things actually get but the problem is people with these units either don't have TDS meters, don't know how to use them, or are to lazy to.
FB
Fishbulb2
New member
<a href=showthread.php?s=&postid=8915655#post8915655 target=_blank>Originally posted</a> by Entropy
This is a pointless arguement since I can probably find just about any type of RO/DI unit being used right now (including what you are using) on eBay sooner or later.
I know you can . I use a frankEnBAY unit (EBAY unit with upgraded components)
FB
PS. I wouldn't recommend it
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