A little story about a EBAY RODI.

[dngspot]

I thought why not a membrane is a membrane and filters are filters. And for the most part this is true. Building a RODI unit is really not rocket science.

When I received the unit, I installed it, and was making RODI water in about an hour. The installation was easy. The output was lower than I thought it would be, the unit was supposed to be a 100 gpd. and was putting out about 60. I did not get to alarmed; my water pressure is at the lower end of spec, 40-45 psi.

About a month went by and I had to know what the TDS output was. I bought an inline TDS meter and hooked it up. I saw 500 in and 30 out. I thought, with a DI canister the TDS should have been around 6 to 0. If the system was shutdown by the auto shutoff the TDS would clime to 150. It would take about 32 oz. of water to get the TDS back to 30.

I bought a set of gauges and installed them, one in the input of the sediment filter and the other in the RO housing. When the system was running the pressure on both of the gauges were even, this indicated that my filters are not plugged. I tested for chlorine with a pool chlorine test kit and found 0. This was not acceptable and I was not going to stop until the TDS output was 0-6.

Thinking that I must have had a damaged membrane, I ordered another one. Wile waiting I found a page on the web that talked about TDS Creep. TDS Creep is solids moving to the output side of the membrane when there is pressure on the output side. This happens when the auto top off shuts the water off. Okay I figured that I was going to have to live with the TDS Creep and am going to have an extra membrane.

After I ordered my unit I found that another was offered with dual DI canisters. These canisters are clear with blue ends. They are not similar to the standard canisters found in systems like Kent. They are refillable which I thought and still do think is a good idea. I had to order another filter kit to get the other DI canister. I installed it and found no difference, still a TDS of 30.

I then hooked up my output TDS sensor to the output of the RO membrane and found no change. This is it. The DI resin that came with the unit new is CRAP. It was not removing the rest or any of the solids.

I went back to EBAY and ordered 1.5 pounds from H20Slash. They are fairly close to me so if their stuff is CRAP, I could knock on their door. I emptied the canisters and refilled them with new resin. Fired it up and the TDS output was 0! It is even 0 when the system is shutdown, no TDS Creep is showing up after the DI canisters.

Message here is, do not expect the little guys with the no name product to do research and development or even quality control. The unit I have is not a non workable unit. It just had CRAP for DI resin.


The original unit cost $99.50 with shipping.


What I should have got at $103.49


What I have now. Priceless


If you do get one of these units order the resin from H20Splash and dump the new stuff. Its about $19.00 shipped. http://cgi.ebay.com/Color-DI-Resin-f...QQcmdZViewItem

[jgrossman]

thanks for the story. I have just purchased a similar unit from filter direct. It looks more like the one in the second picture. I noticed that you took the horizontal DI chambers and mounted them vertically. I have posted other threads wondering if anyone has done this and had success with it. It looks like you did. Again thanks for the log.

[justinm0424]

Hey,
I have that second one. I don't have a TDS meter but I borrowed a friends once and it was about 2-3. I guess i'll have to buy that diy resin. Also my said it puts out 125 a day and it puts out 5 gal an hour which is about 125.

[dngspot]

Originally posted by jgrossman
thanks for the story. I have just purchased a similar unit from filter direct. It looks more like the one in the second picture. I noticed that you took the horizontal DI chambers and mounted them vertically. I have posted other threads wondering if anyone has done this and had success with it. It looks like you did. Again thanks for the log.

During my adventure with the RO/DI I thought that having the unit upright with the water entering both from the bottom would keep the resin from channeling. To be honest I think it has done little good.

[orlenz]

something I noticed,
did you wait a month to check your TDS?
if so it could be that your DI resin was okay when you got the unit, those DI Cartriges you have dont last very long especially with a new system,
a membrane upgrade could add life to your DI, perhaps a filmteck 75 GPD, it has a much higher rejection rate,
another thing you can look at is adding another carbon block before the RO, and a couple full size DI canisters at the end instead of those little inline ones, something like a couple of these,





it would make maintenance much less of a chore. and you will have zero TDS with very little effort on your part.

[dngspot]

Originally posted by orlenz
something I noticed,
did you wait a month to check your TDS?
if so it could be that your DI resin was okay when you got the unit, those DI Cartriges you have dont last very long especially with a new system,
a membrane upgrade could add life to your DI, perhaps a filmteck 75 GPD, it has a much higher rejection rate,
another thing you can look at is adding another carbon block before the RO, and a couple full size DI canisters at the end instead of those little inline ones, something like a couple of these,
it would make maintenance much less of a chore. and you will have zero TDS with very little effort on your part.

The two DI canisters volume is about the same as the DI filter shown. The canisters have additional resin because they do not have the hole in the middle of the filter. Both canisters took 15 oz. of resin. I am not sure how much the one above weighs.
I have seen the advertisement that changing the resin is a chore. I did not find it to be that troublesome, it took about 15 minutes including removing them from the system.

[dngspot]

Originally posted by orlenz
something I noticed,
did you wait a month to check your TDS?
if so it could be that your DI resin was okay when you got the unit, those DI Cartriges you have dont last very long especially with a new system,
a membrane upgrade could add life to your DI, perhaps a filmteck 75 GPD, it has a much higher rejection rate,
another thing you can look at is adding another carbon block before the RO, and a couple full size DI canisters at the end instead of those little inline ones, something like a couple of these,





it would make maintenance much less of a chore. and you will have zero TDS with very little effort on your part.

I would also like to mention, when the second DI chamber was installed and then a TDS reading was made. It was left this way for a week before any change was made to the system. The TDS behaved the same, as if I did not make a change. I would then say, the problem wasn’t because the resin was being depleted in a month, it never worked at all.

[hipertec]

how much was the extra clear case housing and did it go at the last stage?

[BeanAnimal]

Originally posted by dngspot
I thought why not a membrane is a membrane and filters are filters. And for the most part this is true. Building a RODI unit is really not rocket science.

This is the first HUGE misconception. There is a WORLD of difference between membranes. (we will talk about other components later). The "eBay" units use GE DESAL or APPLIED MEMBRANES or KNOCK OFFs of the true DOW FILMTEC membranes. The 75 GPD DOW FILMTEC is has a 98% rejection ration. The GE and others are 90%. They FILMTECS are rated to be used at typical household pressures and do well at low pressures (30 PSI even). The "other" membranes are to be run at 70 PSI to get the rated specs out of them. WORD OF DIFFERENCE.

For those that can not do the math. Given 200 TDS input, the FILMTEC will output 4 TDS, the DESAL will output 20 TDS. That means that right off the bat, the unit with the FILMTEC will use 1/5 the amount of DI resin over the same period that the others will. This simply means 5 TIMES the operating cost... PLEASE READ THAT AGAIN. FIVE TIMES THE OPERATING COST.

So no.... it's not rocket science, but it is science and very predictable.

The output was lower than I thought it would be, the unit was supposed to be a 100 gpd. and was putting out about 60. I did not get to alarmed; my water pressure is at the lower end of spec, 40-45 psi.

Rember these membranes perform even worse at below 70-80 PSI. You will get noewhere near 100 GPD and the rejection ration will be poor (as well as the self cleansing atributes of the membrane).

About a month went by and I had to know what the TDS output was. I bought an inline TDS meter and hooked it up. I saw 500 in and 30 out. I thought, with a DI canister the TDS should have been around 6 to 0.

NOPE!!!!! The membrane is performing EXACTLY as EXPECTED. 500 in 30 out is about 94% rejection... actually pretty good for the mis-used membrane.

If the system was shutdown by the auto shutoff the TDS would clime to 150. It would take about 32 oz. of water to get the TDS back to 30.

This is called TDS creep and is expected. I promised we would talk about the other components... here we are. Because the unit uses poor quality filters and components. The TDS creep os more pronounced. The DI bed is not well designed and will tend to bypass a lot fo crap to the output side.

I had to order another filter kit to get the other DI canister. I installed it and found no difference, still a TDS of 30.

Remember your TDS output of your membrane is very high and very exhaustive on the DI resin. What else can I say...

I then hooked up my output TDS sensor to the output of the RO membrane and found no change. This is it. The DI resin that came with the unit new is CRAP. It was not removing the rest or any of the solids.

Umm there is no solids to remove.. DI resin is ION exchange. The pre filters in thea cheapy units are ...well junk. The resin in the cheapy units is the cheapest stuff they can find. Not all Resin is created equall.

Not to make you feel bad, but at this point I would have hoped your own reaizations would have steered you towards a reputable vendor. You have save NO MONEY by buying an el-cheapo unit.

[B]

Message here is, do not expect the little guys with the no name product to do research and development or even quality control. The unit I have is not a non workable unit. It just had CRAP for DI resin. [/b

I feel bad that you (and thousands of others) have had to learn the hard way. Not all RO/DI units are created equal. Buy a top quality units (around $200-$300) and it will save you many times that in the long run.

I should add that if you do not have a DOW FILMTEC 75 GDP membrane, you are going to burn through resin at FIVE TIMES the rate of those with the better membrane.... so your still not out of the woods.

PurleyH20.COM
BuckeyeFieldSupply.COM
AirWaterIce.COM
FilterGuys.BIZ

Any of those 4 ompanies are honest and sell top quality products and consumables. The bottom line is that you get what you pay for. There are dozens of scam artists selling CRAP on eBay.

Your TDS is 500, that is fairly high, again I would consider the DOWN FILMTEC 75 GPD membrane AND NOTHING ELSE. The $50 cost will save you that much in a very short amount of time.

Bean

[dngspot]

Been,
These may be very fair observations from your point of view. I did not mention what type of filters came with this unit. All filters had water quality stamps. As best as I can tell they are the same filters that are found in a Corallife unit. At this time it is unfair to say most of the water is pasing over the sides of the DI, when I am obtaining 0 TDS. During my inspection of my unit I checked out other units and found Filmtec behaving the same with the same TDS Creep, I have seen them at the same TDS levels. You are correct it does have a Desal membrane. Compairing a 100 gpd to a unit that produces 75 gpd should not be done either. It is common knowledg that a higher production membrane less effecient than a lower production membrane. Time will tell how well the resin last, but I will be here to let you know.

[dngspot]

From Dow own spec sheets a tw30-1812-100 has a minimum salt rejection rate of 90%.
The GE Osmonics Desal TFM-100 have a minimum salt rejection rate of 96% This also came from GE's tech sheets. So far it looks like the Desal will hold its own. As I mentioned in my first post I do not think that the unit is a non workable unit, it just had CRAP for resin.

[Roland Jacques]

I have three GE desal 75 GPD membranes on my RO. all are better than 98% rejection rate. after 2000 gallons at 80 PSI. i requested 75gpd and not the 100gpd and they have work perfectly so far.

i dont recomemed my brand RO because the prefilters are poor quality.

[dngspot]

Originally posted by hipertec
how much was the extra clear case housing and did it go at the last stage?

The additional housing came with a set of replacement filters $27.00, with shipping. I did email the guy and he said that he would sell me one for $10.00 I forget what the shipping was.
Yes it did go to the last stage.

[BeanAnimal]

Originally posted by dngspot
Been,
These may be very fair observations from your point of view. I did not mention what type of filters came with this unit. All filters had water quality stamps.

Not to nit pick here... but I can call a manufacturers clearing house and get 28 gauge wire with .001 mil insulation and have it labled "UL/LISTED 2 Trillion Volts" The factory in china will put anything on it I want, as long as they get paid. The pre-filters may be the same. However, your main problems were 1) the RO membrane and 2) the origianl DI and likely the way it was packed (horizontal I imagine as well?)

At this time it is unfair to say most of the water is pasing over the sides of the DI, when I am obtaining 0 TDS.

Ahh but you WERE getting 30 TDS out of the DI output, which was the same as the RO output. That is either BYPASSING in a BAD way, or fully exhausted resin in a short period if time. Either way it speaks to the quality of the "eBay" units.... which in the end was your basic point as well. Not beating you up, just trying to make it clear to all the readers that the "eBay" units are pure junk.

During my inspection of my unit I checked out other units and found Filmtec behaving the same with the same TDS Creep

All membranes will show sines of TDS creep, it is the nature of the beast. That is why we want to run the unit as long as possible instead of in short bursts.

, I have seen them at the same TDS levels. You are correct it does have a Desal membrane.

The Desal membrane is inferior to the genuine filmtec. As I stated 1 unit has a 90% rejection, the other 98%. One is a "nano filter" the other is a true DI membrane.

Compairing a 100 gpd to a unit that produces 75 gpd should not be done either. It is common knowledg that a higher production membrane less effecient than a lower production membrane.

Even if you take the GE DESAL 100 and the FILMTEC 100, the FILMTEC will win hands down. It is designed to run efficiently over a much larger pressure range. (The low end is where we are concerned 30-90 PSI for residential use). At household pressures, the 100 GPD membranes produce little more than the 75 GPDs. The FILMTEC 75 is what you want to be looking at and forget the 100s, esp with your 500 TDS input.

Time will tell how well the resin last, but I will be here to let you know.

No need to wait. A simple calculator is all that you need. Like I said, the 75 GPD filmtec is 98% rejection, and the DESAL 75 is 90% rejection. That is a VERY SIMPLE ratio 5:1 If you want to get picky, lets just you get 96% of the FILMTEC and 94% out of the DESAL (bad lot on the filmtec and extra good lot on the desal) Your still at 20 TDS to 30 TDS output. That means that you will use resin at 1.5 times faster in the unit with the DESAL.

This is all without talking about the waste ratio and actual efficiency due to pressure (where again the filmtec is far better).

Plain and simple the GE DESAL membrane costs significantly more to run in an RO/DI system. At best it is 1.5 times more costly over the life of the unit, at worst it is at LEAST 5 times more costly. Very simple math

Again, I am not trying to beat you up.... but I also want to make sure you and others understand that this is not OPINION (which everybody keeps trying to frame it as). It is a simple fact of how these products operate. The quality filters, housings, support and all that other stuff are peripheral issues that don't really even need to come into play to understand why the $99 units are a complete waste of money.

[BeanAnimal]

Originally posted by dngspot
From Dow own spec sheets a tw30-1812-100 has a minimum salt rejection rate of 90%.
The GE Osmonics Desal TFM-100 have a minimum salt rejection rate of 96% This also came from GE's tech sheets. So far it looks like the Desal will hold its own. As I mentioned in my first post I do not think that the unit is a non workable unit, it just had CRAP for resin.

I think you need to look a little deeper at the rest of the numbers. That is EXACTLY what the filterdirect people try to pawn off on uninformed buyers. Also, I want to stress, that the 100 GPD membranes are NOT WORTH the extra cost. I don't understand why this is not obvious. Please go compare the 75 FILMTEC to the DESAL 75. It's all about operating cost. If you need higher ouput, it is still cheaper to put 2 FILMTECS in series and cut your waste in half. It's all about operating cost!

[jay24k]

I bought mine from aquasafe and I have 0 issues. TDS is 0 and I only have to change my DI maybe every 6 months and we drink the water too. My TDS is 150 prior to going into the unit. I've had it for about 2 years now and have not had to change any of the other pieces yet. I probably will just to but still showing 0 TDS. That unit that you originally have does look cheap though.

[dngspot]

Bean,
When we consider apples to apples and test the Filmtec’s 100 gpd unit to my Desal 100 gpd the rejection rate of the Desal is 96% and the Filmtec is 90%. Look at the product spec sheet. After this feel free to pull out your calculator and do the math. I am running in the
Desal PSI range. So I feel that a broader range is not of importance to me. Furthermore Filmtec did not mention their test pressure and Desal did. I simply could care less about the 75 gpd units this is not what I have. Please read the rest of the forum, I said that I installed a new DI canister and still had the same reading as with out it, my TDS unit is inline so I get a reading immediately. To have DI resin fail this quickly is and should be uncommon. And I agree with this fact. I simply do not know how the membrane was shipped, if it is falsely labeled. I have two of these membranes from different sources and they look identical, including the packaging. I am not in the position to challenge the credibility of the membrane and because you get bad wire don't blame Desal for the wire manufacture’s false claim. The 500 to 30 are estimates both numbers clime and fall during operation. 94% is acceptable to me and fits in the spec sheets + or - range. As diligently as you are working this unit over, I can only wander if you work for a LFS, Filmtec or a RO manufacturer?

[dngspot]

Jay,
Aside from the filters on the top my unit looks just like the Aquasafe.

[BeanAnimal]

*shrug* no matter how you spell it out, people just don't seem to grasp the simplicity of these units and how they operate.

Jay:
Lets assume we have identicle units with the excpetion of the membranes:
150 TDS into a 90% membrane (the one on your unit) = 15 tds
150 TDS into a 98% membrane (the one on my unit) = 3 tds

We both get 0 TDS water but my resin will process FIVE TIMES the volume of water that your resin will. You change resin every 6 months, I change resin over 30 Months. Lets say resin costs $15 per refill. In 5 years you will spend $150 on resin, and I will spend $30 on resin. The NET DIFFERENCE is $120 dollars over 5 years. Your somewhat LOW input TDS makes the payoff somewhat distant. In that regard, you are not anywhere near being in the same boat as the OP.

500 TDS into 94% membrane = 30 OUTPUT
500 TDS into 98% membrane = 10 OUTPUT

Lets assume we are making the same amount of water as you are with your 6 month example. That means his resin would last 3 months at that volume and mine would last 9 months. So in 5 years he would change resin 20 times and I would change resin 6.6 times. His cost $300 and my cost $100. A net difference of $200.

As you can see the higher the TDS, the sooner the payoff due to the higher operating costs.

There are several other differences between the bargain basement units and the better units. Many of those differences have been pointed out dozens of times here.

I am glad your happy with your unit. I would suggest when it comes time to replace the membrane, that you pruchse the FILMTEC 75 GPD. It is the same price is the DESAL but will cost you less to run.

[jay24k]

I agree the 75 is better. I'm just saying not all ebay units are junk. I'll be going to the 75 because I'd rather save the price on DI. I've only changed my resin once since I've gotten it but I didn't use it very heavily. On my 180, it is used quite a bit more.

I don't need the extra theoretical 25 gpd and that is why I'll drop to a 75.

[dngspot]

I think you need to look a little deeper at the rest of the numbers. That is EXACTLY what the filterdirect people try to pawn off on uninformed buyers. Also, I want to stress, that the 100 GPD membranes are NOT WORTH the extra cost. I don't understand why this is not obvious. Please go compare the 75 FILMTEC to the DESAL 75. It's all about operating cost. If you need higher ouput, it is still cheaper to put 2 FILMTECS in series and cut your waste in half. It's all about operating cost! [/B][/QUOTE] My information did not come from filterdriect, it came from the membrane manufacturers. If I spend another $17.00 for a new bag of DI resin every three months I will still be ahead if I buy a $45.00 cartridge from the LFS and it last 6 months. I have had the new resin in my canisters for 2 months and still get 0 TDS. How long does your calculator say I have left?

[dngspot]

Bean,

At no time did I feel that I did not get it. Nore will I consider you do.

[dngspot]

Filmtech says that their 100 gpd membrane gets a minimum 90% rejection rate. Not 98%. I DO CARE ABOUT A 75 GPD UNIT. This forum was not started to compare a 75gpd unit with a 100 gpd unit. I bought a 100 gpd because this is what I wanted not a 75 gpd.

[BeanAnimal]

I never said the membrane was falsely labled. You mentioned the othe filters being of high quality. I know for a fact that there are plenty of "knock off" filters being sold by many of those vendors.

I did not get BAD wire. I am telling you that many "eBay" items are made overseas and are knock offs of good products. The "specs" on them are bogus and simply printed to match or beat those of the real thing. This includes Carbon and GAC filters, air pumps, water pumps, roto zip tools, computer hardware, car parts, electronics parts, and everything else under the sun. It was just a polite warning to not beleive everything you read on eBay.

I never said that you were not getting 0 TDS, please don't keep infering that somehow I think my 0 TDS is better than your 0 TDS. I AM SAYING that MY 0 TDS COSTS LESS TO MAKE. Thats all.

You also seem to be stuck on comparing 100 GPD membranes. Again, you missing the BIG PICTURE. The DOW 75 membrane outperforms the DOW and DESAL 100 GPD membranes by a long shot. I could care less about the dow 100 GPD membrane, its a hunk of crap and not really a RO membrane anyway. It's a NANO FILTER. The POINT is that you would be better off with the DOW 75, it would cost less to run. You would get nearly the same output out of it. It's that simple.

Please reread this until you understand where I am coming from. It's not opinion, just very simple fact. I am not disputing your numbers or that fact that you may be happy with 94% rejection instead of 98%. Some people are happy with 10 miles to the gallon and others are happy with 30 miles to the gallon. You are saying you can't compare a truck to a hybrid. I am saying I don't care, one gets better mileage than the other and if your concerned SOLELY about COST, then there is ONLY 1 choice.

Lets put this into 2 simple statements.

If you care about the total cost of ownership, then you have the wrong membrane.

If you don't care about the operating cost and value the few extra gallons a day, then you have the right membrane.

I am not trying to persuade you to change... I do however want to ensure that people who read this understand the VERY SIMPLE difference.

See how easy that is

Thanks for the conversation and good thread. I am glad you got your unit operational... your livestock will surely be much better off now.

[BeanAnimal]

Originally posted by dngspot
Filmtech says that their 100 gpd membrane gets a minimum 90% rejection rate. Not 98%

PLEASE I NEVER SAID IT DID!!!!!!! the 75 GPD membrane is 98%. The 100 GPD membrane is 90% and not really the same kind of membrane.