Does anyone run double DI Resn?

[Latinreefer]

I really want to generate water with zero TDS and I'm having trouble. I run a 150 GPD system with a pump 6 stage and I can't get aero TDS right out of the system before I store the water. I put the water in a clean glass as soon as it comes out and my TDS is 0.50. I run one di resin at the end of my system and I'm considering running a 2nd canister with di resin. Does anyone run two di resin in their systems? I run double membrane as well. Give me some input.

Thanks

 

[Nitr8]

I run double DI resin canisters. TDS is always 0 and usually 1-2 before going into the DI resin.

 

[TwistedTiger]

I run a double DI system, but there is no way you should be getting anything above 0 TDS unless either your DI is spent or you have severe channeling. I would look at whether you have the proper setup for you're water system or if you have it set up correctly. If very soon after changing DI you get higher than a 0 reading there is something wrong.

 

[Planedoc]

I just started running two. When I get above 1 tds out of the first one a replace it with second one and put new resin in the second. I just started but I think it's going to save me 50% on the cost of resin.

 

[yellojello]

What's your incoming tap water TDS and after membrane before DI TDS?

I just added a second DI as a fail safe, but switched my 100gpd membrane with about 96% rejection rate to the 90gpd membrane about 98% rejection rate. Although making water is a wee bit slower, my after membrane TDS went from 14-16 tds to 7-8 tds. This pretty much makes my DI last about twice as long. Incoming tap water is about 340-360 TDS.

A problem I had a long time ago was that the membrane housing was not screwed on tight enough... water would not leak, but was about 1/2 to 1 turn loose, which may not seal the membrane fully to get the best filtration.

I do the same as Planedoc. Using color changing resin, when my second DI starts changing color, I move the second DI to the first, and refill and put the new one in the second.

 

[choff]

I run 2, but only so I can run the first one to complete exhaustion then I move the 2nd unit into slot 1 and put fresh resin in Slot 2.

What is your tds going into the resin chamber? Is your Di chamber packed as tight as humanly possible? You should not be getting any tds coming out.

 

[Nitr8]

I run 2, but only so I can run the first one to complete exhaustion then I move the 2nd unit into slot 1 and put fresh resin in Slot 2.

What is your tds going into the resin chamber? Is your Di chamber packed as tight as humanly possible? You should not be getting any tds coming out.

+1.

 

[Latinreefer]

Thanks everyone for your input. I wasn't to clear, the water that goes into my resin per dual TDS meter is 1-0, then after the resin the meter says 0. This seems to be the norm here but what I failed to say was that after it comes out of my resin I put some in a clean glass and check it with a handheld TDS meter and that gives me a reading of 0.50. The dual meter says 0 after the resin, the handheld is 0.50. I calibrated the handheld so I feel its more accurate than the dual thats in the line of my rodi set up.

 

[Latinreefer]

So what I was wondering if anyone had doubled check the TDS with a handheld and if they feel a need to run double resin to get lower tds.

Thanks

 

[motortrendz]

I actually added a second di resin as well as a po4 reducer as the final step.

 

[choff]

I run my rodi line into a 60 gal barrel with a loose fitting lid. The water will sit at the longest for a week. I have used a handheld TDs meter often because I have 3 online TDs meters and do get varying results from them. One thing is to make sure your inline tds meter pins are aligned properly. I think both pins are supposed to be in series alignment with the flow (vs side by side), but please confirm that.

On my handheld I will get tds readings above zero in my collection barrel if I test the top undisturbed layer, but if I mix up the water and retest I get zero. I attribute this to whatever environmental crap floating in the air is landing in the top skin of the water. When mixed into 60 gal its undetectable levels.

 

[cdness]

The handheld will be more accurate. However the way people have described the dual DI is the way to go so you can save on resin and have a safety. You should get to 0 after the DI whether you have a single or double DI unless you have exhausted the DI or it has channeling... I run dual DI...

I can say once you place the water in a container, even a clean class, you may pick up some TDS.

 

[AZDesertRat]

What is your tap water TDS, RO only TDS and RO/DI TDS?
What are you using for a TDS meter and has it been calibrated or at least tested in some distilled water to see if it is at all accurate? Do you triple rinse the TDS meter in RO/DI or distilled water after each use so it stays clean and capped when put away? Is the glass you are using a clean, clear glass drinking water glass washed by hand in very hot water so it has no dishwasher soap residue or anti spotting agents to skew the TDS readings then triple rinsed in RO/DI or distilled between and after each test so it too stays clean?

What filters, RO membranes and DI resin are you using and do you keep up with the minimal maintenance on the system such as filter replacements and annual disinfection? Is the resin fresh and if bought in bulk properly vacuum sealed and stored in the refrigerator to keep it fresh for up to a maximum if 6 months?

How do you have the membranes plumbed, series or parallel and what is your exact measured waste ratio? What is your water temperature and what pressure are you running the booster pump at? Is the booster an Aquatec 8800 or equal so it can keep up with the flows of dual membranes? If it is an Aquatec 6800 or equal it will not do so. Do you make RO/DI in large batches or in short spurts?

I have two dual inline TDS meters and never even turn them on since they lack low end accuracy, my two handhelds are always close and accurate since they are temperature compensated while the inlines are not. I do run dual DI and have for about 12 years now with 0 TDS from both DI cartridges, when I see anything other than that it gets changed out.