Reef nutrition

Turning an RODI unit to a DI-only unit

itsacrispy

itsacrispy

Guest
BARcard
Hi all,

Well I took another hit due to water-usage last month, so I'm thinking about turning my RODI unit into a DI-only unit. My TDS in Danville is 33, so I think it should be OK to go DI-only. There are a few questions I have though, and I was wondering if you guys could help me out:

1. I have one of Melev's (Marc) 100 GPD units, is it even possible to do this conversion? I've put an email out to March, but he's quite busy and I'm hoping someone here has experience doing this.
2. I know my DI cartridge would degrade much faster, but does anyone have an idea how much more frequently I would need to replace it? I do weekly water changes of 15 gallons, and top off about 3 GPD. That translates to roughly 150 gallons in water usage a month.
3. Do I need to dechlorinate water from a DI-only unit?
4. What does the DI unit NOT remove from tap water?

Thanks a bunch guys, I really appreciate your time and attention to this.

Mike
 
This is what I would do, if I had decided to convert my RO/DI into DI only.

First, I'd keep all the pre-filters. Then I'd BUY two more CLEAR filter housings AND two empty filter cartridges. I'd (bulk) buy colour changing cation and an anion resins and fill each of the two with one of those.

I'd keep an eye on when the colour changed on them, then recharge as necessary (or replace)

Some resources;

Ah, well you can just buy this, then replace the RO unit with two of these kits;
http://www.airwaterice.com/product/ADDVERTDI/Vertical_Color_Changing_DI_Adder_Kit.html
And this http://www.airwaterice.com/category/11/

I chose that site since they are a sponsor. True SpectraPure too, since I think they are also a sponsor.

http://www.spectrapure.com/St_di_systems.htm

V
 
As to how much faster... depends upon your rejection rate, if you have 95% from your membrane, you'd basically burn through resin 20x faster since before only 1 part in 20 was getting through, now 20 out of 20 is going in.

Also something to keep aware of is that I believe contact time is important for resin as well as your carbon filtration, so you'll need to slow the water down most likely some how. Might be wrong on this though so do some research first :D
 
Thanks guys.

Vince, I apologize for my naivete, but I'm having a difficult time picturing what you posted. I think you're telling me to just turn the RO/sediment filters into DI units. So basically, I would have a total of three DI units. Is that correct?

Thanks!
 
Well, actually I'm saying to keep the pre-filters of your current unit, then basically build/buy a new dual resin DI unit. That way the prefilters can get rid of most junk, then let the DI resing do it's work.
I assume you have 3 prefilters?

Basically replace the RO membrane part with dual DI is what I'm saying, so you'd have

3 prefilters
(removed RO membrane housing)
1 cation di resin filter
1 anion di resin filter

Alternatively, you CAN turn two of your current pre-filter housings into DI resin holders so you'd have;

1 prefilter
1 cation di resin filter
1 anion di resin filter

With DI, you CAN recharge them. With colour changing resin, you can SEE when that needs to happen. Someguy did a great write up on recharging resin. Even the seperating a mixed bed resin was easy (in one solution, one resin sinks while the other floats, so you just scoop up one type of resin to seperate it.

Start here for recharge stuff
http://reefcentral.com/forums/showthread.php?threadid=1144161

Good luck!

V

PS. I knew Mike would chime in as I remember he was going to do this.... then figured it was not worth it??
 
I did the same thing. Chop out the RO membrane, and plumb the prefilters (you can get carbon cartridges that take care of chlorine) to a Dual DI set up. Actually, I run from the prefilters to a 20 inch DI canister that runs to 2 clear DI canisters that are filled with color changing resin. You can actually run the water through the DI resin pretty quick if you want to.

http://www.bulkreefsupply.com/RO/DI-Filters-&-Systems-Large-Systems/c9_94/p454/Jumbo-20%22-DI-System/product_info.html

and

http://www.thefilterguys.biz/di_systems.htm
 
Wow, thanks guys. I actually thought the RO membrane was the same as the pre-filter...shows you just how much I know about RODI units. I get it now though, and thank you guys for clearing this up for me.

I'll have to check when I get home, but I assume it's basically a "plug-and-play" situation right? Basically:

1) Unplug the line from pre-filter to RO membrane.
2) Plug the same line into a DI unit

If that's the case, might I ask what the harm is by just going straight to DI? I notice you both add an extra DI unit in the system, is it for redundancy or slowing down the flow a bit, like what sfuphysics suggested?

Thanks again for your patience guys, I really appreciate this.

Mike
 
There are two different types of resin "Cation" and "Anion" my brain can't go back far enough in time to high school chemistry, but I believe one is good at capturing positively charged ions, and the other is good for negatively charged ions. This way you capture all those pesky ions.

The prefilters will save your resin (and money) as they filter out larger particles. (bigger than ions, like rusty pipe particles, and mosquito egg particles and cryptosporidium etc etc)

V
 
You must log in or register to reply here.
Back
Top