Ebay RO/DI Units...
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AZDesertRat
In Memoriam
They are +/- 2% of full scale which is 1-1000 so they can be off by 20 ppm. Thats true of almost every hobbyist grade meter.
RobbyG
Active member
The meters are very inaccurate and my personal observation from reading many Ro related posts is that people with Dow 75 membranes typically get outputs of 5ppm at 250ppm+ Input. So more than likely a 500ppm+ input should result in a 10ppm+ output.
Now some math seems to back that up since Dow says the rejection rate is 98% so for each 100ppm IN you should get 2ppm contamination OUT. So 2ppm per 100 times 500+ he is inputting would give you 10ppm+ expected output reading. Of course water pressure etc. will change that some what, but as I said I mostly based my statement on readings that others have posted before.
And as I stated before I am no RO expert but I do know cheap equipment when I see it.
RCS
In Memoriam
Guys/gals, I need to throw this in here, because I see a lot of "long-term cost of ownership" numbers being tossed around, and have a serious problem with the way they're being calculated.
I've had an AWI unit in the past (nice unit, no problems) and currently have a $92 Ebay unit (nice unit, no problems). I would say both units are "fine". That doesn't mean the most expensive, that means I get good results when I use them in my circumstances. End of story.
BTW, the whole line of figuring out the "added cost" of a lowered rejection rate is kind of silly, considering for that $38 you can swap out the membrane and get the same performance. Why would you pay an extra $200 or more up front for that?
I think some people are caught up in the idea that more expensive equals higher quality. It's not always the case, and I can't see spending that extra money up front...even if in the long run the costs equal out, I'd rather save $100 up front and spend an extra $5 or $10 here and there doing minor "upgrades" to a unit over time.
BeanAnimal, every line of calculation I've seem from you considers the fact that the user is too stupid to replace a membrane with something better (which, if you've got two hands and at least one opposable thumb, shouldn't be difficult). If you replace the membrance at a cost of $38 as I stated above, then your math is a moot point, and cost of operation is about the same long-term, only you save money up front.
So, I can conclude either you think everyone else who has an RO system is stupid, or you just really, really, really like spending extra money on questionable items, and feel the need to try and get everyone else to as well.
I've had an AWI unit in the past (nice unit, no problems) and currently have a $92 Ebay unit (nice unit, no problems). I would say both units are "fine". That doesn't mean the most expensive, that means I get good results when I use them in my circumstances. End of story.
BTW, the whole line of figuring out the "added cost" of a lowered rejection rate is kind of silly, considering for that $38 you can swap out the membrane and get the same performance. Why would you pay an extra $200 or more up front for that?
I think some people are caught up in the idea that more expensive equals higher quality. It's not always the case, and I can't see spending that extra money up front...even if in the long run the costs equal out, I'd rather save $100 up front and spend an extra $5 or $10 here and there doing minor "upgrades" to a unit over time.
BeanAnimal, every line of calculation I've seem from you considers the fact that the user is too stupid to replace a membrane with something better (which, if you've got two hands and at least one opposable thumb, shouldn't be difficult). If you replace the membrance at a cost of $38 as I stated above, then your math is a moot point, and cost of operation is about the same long-term, only you save money up front.
So, I can conclude either you think everyone else who has an RO system is stupid, or you just really, really, really like spending extra money on questionable items, and feel the need to try and get everyone else to as well.
RCS
In Memoriam
Ever think that maybe they're not rejecting as much stuff then? Or can it only be because they're "bigger"? Ever considered that maybe they SHOULD be dirtier? I'd be more worried about a clean prefilter than a dirty one.
Have you considered the potential difference in micron rate as well? The above is one of the worst junk science statements I've read in a long time, and really has no value or validity whatsoever.
AZDesertRat
In Memoriam
A $38 membrane does not get you 99.25% rejection unless you are very lucky. Yes an occasional one comes out in excess of 98% but its very rare and is not guaranteed to do so.
BeanAnimal
Premium Member
Why must you guys preface everything with a personal attack, grow up. To make matters worse, you just shoved your foot in your mouth again.
I suggest looking up the definition of "Full Scale" accuracy and how it is measured. They key term being FULL SCALE. This is a VERY BASIC skill needed to be able to understand the signifigance of any meter or measurement device.
Good grief.
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BeanAnimal
Premium Member
Where exactly do you think I got the numbers I used? FROM THE SPECTRAPURE AND THEFLILTERGUYS WEBSITE. I suggest taking another look. I not only showed the math, but the cost of each component used.
This is starting to get very old.
BeanAnimal
Premium Member
Yet you have not explained what the problem is or why the math is wrong....
and the record skips to the first track again. One more subjective post. Please define "fine". Are we talking about water quality? Resin usage? Durability? Customer Service? What are we quantifying here?
You do NOT pay $200 to just get a better membrane. That is a misleading comment and why these threads are as long as they are. DO we really have to rehash this whole thing again? Filter quality?, Component quality?, Resin configuration, Resin Quality, Customer service?, etc. You are free to buy what you want, but please do not insult the rest of us who understand or find VALUE in quality built systems.
No sir, not at all. But in the converse, at a certain price level QUALITY goes out the window. To propose anything different is to be ignorant to economics, manufacturing and business. Hundreds of thousands a people a day get fleeced because they think that bargain products are really a bargain. eBay is the marketplace for such junk.
The PROBLEM is that it does equal out. There are masses of people out there paying out the nose to refill their DI chambers because they purchased junk from eBay. If you do not believe that, then I have a bridge for sale CHEAP.
Firstly MOST users would not even know to change the membrane. Secondly, MOST users would not know what kind of membrane to buy. Thirdly, MOST of the "eBay" vendors peddle lesser membranes but advertise them in a manner that portrays them as superior to the DOW FILMTECS. Nothing like buying from a dishonest vendor! Moreover, it is not a simple $38 difference. You are ignoring all of the OTHER problems with the units.
And your conclusion is baseless and would therefore be wrong.
BeanAnimal
Premium Member
Yup I am sure
RobbyG
Active member
Hmm Lets see
My Ro system has been running for 18 Months, the TDS before DI is consistently 5-6ppm and the TDS after DI is Zero. My Tank phosphates are at almost Zero and I have no algae problems. YEP I am very happy that my prefilters look clean.BTW Mr. Scientist did you Mean "Micron Rate" or "Micron Size"
because I have no idea how fast my microns are travelling:lol:
BeanAnimal
Premium Member
What he was trying to say was that the better filters have more surface area. Therefore, used under the same conditions as a SMALLER filter or one with LESS surface area, the better filter will show less visible signs of use.
Junk science? Where! Did somebody mention global warming?
BeanAnimal
Premium Member
It should also be stated, that the first filter is the one that should show the signs of use as it takes out the large particulate. If the downstream filters do, then have a problem. So no, seeing dirty filter is not a sign that things are working better.
RobbyG
Active member
RCS I am not sure were you are getting those numbers from. I paid about $110 for my Ebay Dvoneb about 2 years ago and I paid $189 for My Typhoon III about 3 months later. That's only a $79 difference and almost all the Parts of the Typhoon 3 are vastly superior to the Ebay unit. Dow Tech Membrane, Clear Prefilter Canisters that are twice the size and made out of plastic twice as thick. Hose connections that are vastly superior, Vertical Refillable DI cartridge that 3 times the Size of the EBay unit. The list goes on and on.
Very old indeed. Me giving you numbers proving that the MaxCap has higher DI costs and you denying that it.
I didn't take into account the initial equipment costs(housings, tubing, brackets) when coming up with my numbers. This is pretty much the only difference between our calculations. Only including media costs is a more valid way of looking at long term TCO in this situation. You could also save more through thefilterguys by purchasing 4 refills at a time.
As far as quality goes, I'm going to ask once more: Show me the conductivity of water produced by the semiconductor grade resin from thefilterguys and the conductivity from the MaxCap.
People keep mentioning honesty among vendors. Did anyone forget that Spectrapure advertises a 75 GPD Filmtec membrane as a 90 GPD membrane? You don't think that's dishonest? I've seen their explanation for it, but I still think it's shady. Also, claiming that the MaxCap will cut DI production costs in half is just a flat out LIE.
BeanAnimal
Premium Member
Read my post again sir (afterall you did quote it) I never denied anything, I simply did the MATH using the products that you mentioned. In all your flailing about to prove me wrong and throw insults, you have lost track of the facts. I simply did the math and noted that a KEY difference (according to the literature) could be the actual output water quality. I also stated that that aspect may or may not be important. Good grief.
I included the DUAL chamber DI setup from Spectra and the DUAL chamber DI setup from TheFilterguys so that nobody would cry foul. Please, read the post again. Furthermore, YOU can't even keep track of what YOU say, let alone me. You most certainly did take into account the cost of the MaxCap. Did you not quote the price and mention that as making the difference even more lopsided.
Huh? I think you need to look up the definition of TCO. Not only that, but I never said that that spectrapures maxcap was cheaper than thefilterguys in terms of TCO. I have not taken the time to examine the numbers, and could frankly care less. We are talking about eBay units compared to the better FILTERGUYS and SPECTRAPURE units. Please, stay focused if you want to fight with me, otherwise you are going to get eaten for lunch
And once again do I need to mention that you just contradicted yourself (remember the comments about the initial cost of the MaxCap). Your starting to flail my friend...
I am sure Spazz or even SpectraPure would be more than happy to. I could care less, as that is a side issue and has NOTHING to do with the main focus here.
How can it be shady when they hand test them to produce at or excede that rate. Come on man, now your digging yourself a hole. What about AMD and PENTIUM Processors? Thousands of CPUS from the same manufacturing run are graded as to their fastest stable operating speed and then stamped as such for resale at that speed. So you 1.6 Gigahertz chip is really a 2.0 Gigahertz chip that did NOT make the cut. What about lumber? It is graded after manufacturing and sorted for sale at different price levels depending on hand selected quality. What about MEAT. It is hand graded after it is CUT and sold at a price level that matches it's quality. Produce? Thousands of products are sold that way. Many times at a different capacity than the OEM rated them at.
Honestly man... just give it up.
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The statement is made over and over again that you will spend more in the long run with the eBay units than you will with a "quality" unit from thefilterguys or Spectrapure. I'm trying to show why this just plain isn't true. Any quality differences below 0ppm are not important. This has been stated by Randy Holmes-Farley over and over again.
I never disputed that you did. In fact you made it pretty obvious from the start.
My point(that you keep ignoring) is that you can take the ebay unit and replace the filters with new ones from thefilterguys and still come out way ahead on cost in the long run.Huh? I think you need to look up the definition of TCO. Not only that, but I never said that that spectrapures maxcap was cheaper than thefilterguys in terms of TCO. I have not taken the time to examine the numbers, and could frankly care less. We are talking about eBay units compared to the better FILTERGUYS and SPECTRAPURE units. Please, stay focused if you want to fight with me, otherwise you are going to get eaten for lunch
So instead of countering me, you are going to dismiss me by saying you don't care?
Flat out wrong again. They only test the SpectraSelect membranes. Not the ordinary Spectrapure membranes. These are simple rebranded Filmtecs with a higher GPD rating stamped on the side. If you were to buy a Filmtec and apply the same pressure and temperature, you'd get the same production. The fact is that Filmtec gave the 75 GPD rating at 50psi to avoid misleading claims. Spectrapure(and all vendors for that matter) should follow that same method.
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