Adding DI stages to an existing ro drinking water system

[1Arrecife]

This is my existing system, I want to "T" off after the activated carbon filter and install a 2 stage deionization.

Two shut off valves will be installed on the line diverting to before and after DI stages. So I can flush away any tds creep in the line from the bypassed storage container by using the faucet and shut off DI water production when not needed.

Any suggestions are greatly appreciated. I have a 38 gal. tank I will be setting up soon, so I don't need to store rodi water since I can produce it fast enough.

Before

After

 

[Quietman]

Should work...I might tee it off before the final carbon filter though. Don't think you'll get any value in running your RO through carbon before the DI. Also, that last carbon block in drinking systems is for improving taste of RO and you likely want that life extended as much as possible.

 

[redfishbluefish]

NO! You don't want to be drawing water from the 3 - 5 gallon storage tank. Want makes this water drinkable (have some flavor (or not taste flat)), is the breakthrough TDS that occurs every time the unit refills the tank.....and that is every time you draw water out of the faucet. The TDS in that tank will burn through your DI real fast. You will want to install the tee valve after the membrane so that now water isn't being fed from the tank, but all coming from the membrane. Let me see if I can find a diagram that shows what I'm talking about......be back shortly.

EDIT TO ADD

Well that was a bit harder then I thought. This was the best I could find without spending too much time, and I'm pretty sure it will get my point across:

Now here's the one change I'd make. After the S/O valve, that first tee I would change to a tee valve. Here's an example from BRS:

With the valve in this orientation, water from the S/O valve comes in from the bottom. With the top two connections, one goes to your storage tank, the other goes to the DI resin. By using this valve, you can get rid of the two single valves in the diagram. Under "normal" operation, the valve is flipped to fill the storage tank. When you're ready to make water for your aquarium, flip the valve and let it rip! When you're done making your aquarium water, flip the valve back. Hope this is clear.

 

[1Arrecife]

NO! You don't want to be drawing water from the 3 - 5 gallon storage tank. Want makes this water drinkable (have some flavor (or not taste flat)), is the breakthrough TDS that occurs every time the unit refills the tank.....and that is every time you draw water out of the faucet. The TDS in that tank will burn through your DI real fast. You will want to install the tee valve after the membrane so that now water isn't being fed from the tank, but all coming from the membrane. Let me see if I can find a diagram that shows what I'm talking about......be back shortly.

EDIT TO ADD

Well that was a bit harder then I thought. This was the best I could find without spending too much time, and I'm pretty sure it will get my point across:

Now here's the one change I'd make. After the S/O valve, that first tee I would change to a tee valve. Here's an example from BRS:

With the valve in this orientation, water from the S/O valve comes in from the bottom. With the top two connections, one goes to your storage tank, the other goes to the DI resin. By using this valve, you can get rid of the two single valves in the diagram. Under "normal" operation, the valve is flipped to fill the storage tank. When you're ready to make water for your aquarium, flip the valve and let it rip! When you're done making your aquarium water, flip the valve back. Hope this is clear.

Wow looking at that diagram made my head hurt a little. Took a while to understand but i see how it works. Appreciate you taking the time. You are right about the tank and TDS, but I don't intend to use it when producing deionized water. If you look at the pressure tank on the diagram, it has a shutoff valve. I would close off the ptessure tank when making DI water. I also intend to flush the line before making DI water using the faucet.
Using that 3 way valve looks very convinient.

The thing I have not taken into consideration is what Quietman said above. Understanding if there's any benefit to running RO water through activated carbon.

 

[Rjramos]

My system has dual output. I understand about TDS creep in the R/O tank water, but that water has been brought down from 160 TDS (tap water) to 7TDS (post R/O membrane). Isn’t it easier and more DI resin efficient to bring 7TDS to 0, than carbon and sediment filtered water significantly higher than 7 to 0 with DI resin?

 

[1Arrecife]

My system has dual output. I understand about TDS creep in the R/O tank water, but that water has been brought down from 160 TDS (tap water) to 7TDS (post R/O membrane). Isn’t it easier and more DI resin efficient to bring 7TDS to 0, than carbon and sediment filtered water significantly higher than 7 to 0 with DI resin?

Everything in all diagrams seen is post RO. Nothing is being run through DI before RO. As you know already, the membrane allows other things smaller things than water molecules to permeate. TDS creep happens as deposits form, settle and begin to accumulate inside the pressure tank over time. If you produce DI water using the tank you are 100% likely to drain it entirely sucking up all the deposits, whereas for drinking purposes you might not even drain 30% of the total capacity of a 3 gal. storage pressure tank in a day.