What's your favorite ro/di unit?

[Buckeye Field Supply]

is there really a difference in RODI units?

guess im confused on how one could pass water better thru the same filter vs the next?

 

After building these sytems for over 15 years, I can tell you w/o a doubt, yes, there is a difference.  And that difference in not limited to the replaceable filters.  I can expand on this if people are interested.

 

Russ

[Buckeye Field Supply]

  I put an auxiliary pump to get more pressure but coupled with the COLD water my output is still not at rated capacity so the system runs a lot to make my water.

Something may be wrong with your system.  For example, let's assume you've adjusted your pump to 80 psi, and you have very cold tap water at 50 F:  With that combination of temperature and pressure, a 75 gpd membrane should produce...  75 gpd.  With water a little warmer at 55 F, a 75 gpd membrane should produce 83 gpd.

 

Depending upon the brand name of your membrane the gpd capacity usually has a plus or minus fundge factor in there - often something like 15%.

 

Russ

[Buckeye Field Supply]

If I were to decide to start again, I would build my own. It should be apparent to you that every company uses the same plastic canisters, the same mounting hardware (basically-but this has no effect on performance) the same plastic water lines, some use slightly better connections, and everything else membranes, filters, tds meters, pressure guages, etc. are all in line products that they themselves add onto the unit.

 

A RODI unit is seriously the most off the shelf product I have ever seen. 

 

Keep the canisters you have, keep the mounting hardware, if you want to add a membrane, get a clip on holder from BRS. Buy the BEST membranes and filters for your needs, get proper size flow restrictors, buy the best in line TDS (but I second the handheld option for accuracy's sake), buy the best pressure gauge, replace all your current fittings with John Guest fittings, get some new water lines if you think it's necessary, add a solenoid, whatever. You now have a product that is most likely superior to all of your pre assembled options, for probably less money, since you reused some older parts.

We'll repectfully disagree with you on this.  There are significant differences in the housings, brackets, pressure gauges, asov's, fittings, configuration, etc.  If you've not held many brands side by side the difference wouldn't be obvious.

 

Russ 

[Mattiejay6]

Der ABT, on 24 Jul 2013 - 08:07 AM, said:

is there really a difference in RODI units?

guess im confused on how one could pass water better thru the same filter vs the next?

 

After building these sytems for over 15 years, I can tell you w/o a doubt, yes, there is a difference. And that difference in not limited to the replaceable filters. I can expand on this if people are interested.

 

Russ

 

----------------

 

Russ,

 

I am interested and would like for you to elaborate as this will really help me make an informed decision on what to buy..

 

Matt

Edited July 30, 2013 by Mattiejay6

[Djplus1]

We'll repectfully disagree with you on this.  There are significant differences in the housings, brackets, pressure gauges, asov's, fittings, configuration, etc.  If you've not held many brands side by side the difference wouldn't be obvious.

 

Russ 

No, you're agreeing with me. As I said, buy the BEST (which would imply "significant differences"), not the same junk that 90% of the manufacturers use. Kudos to your company if you provide a one stop solution and and wish more companies offered more in the lines of quality. 

[firecrackerbob]

Im gonna briefly chime in here- ive wasted too many hours debating this on forums to care about changing peoples minds at this point, but  I will say this- I'm a chemical engineer with access to Agilent 1200 series LC\mass spec and GC\mass spec.  I purchased a el-cheapo ebay RODI system from aquasafe systems for 100$.  Out of the box my TDS was zero.  I took a sample in of tap water, RO water, and RODI water and ran it on LC\mass spec and GC\mass spec.  The RODI water showed only one peak (which I attributed to the resin) that was much beyond the limit of detection of the instrument. 

 

Ive posed this question numerous times with very weak responses- If I cannot get a impurity beyond the LOD of my instruments why would I buy a more expensive RODI unit?  My system has been in service for over 10yrs with no problems providing both drinking and aquarium water.

 

People can spend what they want and fall for the gimmicks of RODI sales companies if they want, but I have yet to see them provide any science to back their claims.

 

As for me, I would recommend the el-cheapo to anyone…

 

Out

[Origami]

Bob, couldn't I get similar results if I just ran the particulate-filtered tap water through a mixed bed resin to get 0 TDS out? Of course, it could be argued that the operational cost of this simple setup is higher than one with, say, an RO membrane (which add acquisition cost that could be recovered over long term operation). What I'm saying is that technical performance is one parameter; acquisition and operational costs also figure into selection equation, though.

[Der ABT]

quality of plastics, defects etc, metal bracket etc i could see being different but those would not affect the performance, just longevitiy unless we are talking about thicker walled tubing etc to help keep pressure up.

i guess layout could provide less pressure drop....few 90deg, less distance between filters but otherwise, its the same filters.....

 

unless they dont pass water thru the filter right, the filter is what does the work....not saying this isnt possible but i dont think its in the majority...kinda like light fixture vs DIY

 

not trying to attack you or your business, ive actually heard really good things about you guys...and that is the last variable.

 

if you buy one and make it, there is no one to complain to....your on your own to fix........if you buy from one of our venders....yuo have support/warranty/etc....

support and warranty go a long way in this hobby and is the main reason i do what i can to buy locally...heck i drive to ashburn for dog food  (with a side of acro's)