DI resin and multiple canisters

[Xtc_link]

Should I add a third canister of DI resin? And is tds creep worth working about? 212tds from the well, 1 1/2cups drained takes it to 4ppm in the Ro housing. Then another 1 1/2cups in DI can A to get it down to 2

 

[Randy Holmes-Farley Verified Community Expert]

I'm not really sure what you are asking.

Almost never would two DI canisters not be adequate to get to 0 ppm TDS. If they aren't doing the job, they are either not packed properly, or are poorly designed. Can you better describe what you are using? I'm not sure what "drained" means.

TDS creep happens through the RO membrane when the water is not running, and is a reason to make larger batches at once over smaller batches. The smaller batches will deplete the DI resisns faster, but it doesn't make it more likely to penetrate two undepleted DI resins.

 

[Xtc_link]

Sorry I should of been more clear with my questions. .

The Rodi system is a Spectrapure maxcap w/99%ro membrane with dual DI chambers. The first chamber is now showing 2 tds, second container is still reading 0. I'm just wondering if a third DI chamber would be worth adding so I can get more water before the first chamber is exhausted. Also at what tds output is it considered exhausted?

I've found tds creep in the ro housing and between the dual DI canisters. Is the few cups of high tds water worth even worrying about? when I say drained. I mean I physically disconnect the clean water line (after the ro housing, then between DI canisters) to bleed the tds creep water down the drain.

Happy Holidays!!

 

[Randy Holmes-Farley Verified Community Expert]

Sorry I should of been more clear with my questions. .

The Rodi system is a Spectrapure maxcap w/99%ro membrane with dual DI chambers. The first chamber is now showing 2 tds, second container is still reading 0. I'm just wondering if a third DI chamber would be worth adding so I can get more water before the first chamber is exhausted. Also at what tds output is it considered exhausted?

I've found tds creep in the ro housing and between the dual DI canisters. Is the few cups of high tds water worth even worrying about? when I say drained. I mean I physically disconnect the clean water line (after the ro housing, then between DI canisters) to bleed the tds creep water down the drain.

Happy Holidays!!

Adding a third chamber won't impact the depletion rate of the first in the series of 2 or 3.

What I do (with two) is when the effluent from the first is getting close to the TDS entering it (meaning it is just about totally depleted), I remove the first in the series, move the second one into the first position and put a new one into the second position. That way you still make good water (1 ppm TDS or less) and get nearly all of the capacity out of the DI resins.

I personally wouldn't worry about TDS creep to the point of draining it, but I do run the RO/DI in large batches to minimize the effect.

 

[rlman41299]

Adding a third chamber won't impact the depletion rate of the first in the series of 2 or 3.

What I do (with two) is when the effluent from the first is getting close to the TDS entering it (meaning it is just about totally depleted), I remove the first in the series, move the second one into the first position and put a new one into the second position. That way you still make good water (1 ppm TDS or less) and get nearly all of the capacity out of the DI resins.

I personally wouldn't worry about TDS creep to the point of draining it, but I do run the RO/DI in large batches to minimize the effect.

I never thought of it this way and it makes a lot of sense. I totally replace both of my di resin when the tds creeps up :-(. What a waste

 

[Xtc_link]

Awesome thanks!

 

[AZDesertRat]

You say you have a MaxCap. Are you using the Spectrapure MaxCap then SilicaBuster DI resin cartridges as it was designed to do? If so you cannot interchange them as the two resin blends are very different and the MaxCap cartridge can only be used as the first cartridge in a dual DI arrangement.
They are designed so you replace the MaxCap cartridge when you start seeing TDS between the two DIs on the IN probe of the right-hand TDS meter. You should go through about 3 MaxCap cartridges before you start to see any signs of TDS from the SilicaBuster cartridge and need to replace it for the first time.
Yes, installing a DI bypass valve and flushing the first bit of TDS creep water is a good investment. TDS creep will be approx half your tap TDS so 4 or 5 ounces of up to 100+ TDS water can make a big difference in DI life.
There is no need for a third DI if your system is working correctly. You say you are on a domestic well system, what is your pressure and do you know if you have co2 in your water? Both have a major effect on how well a RO/DI performs.

 

[redfishbluefish]

I use a diverter valve that I picked up from BRS to run-to-waste the first couple of minutes of water on start up.

On start-up of my RO/DI unit, I get break through TDS of between 50-70. Instead of this burning up my DI, I run this to waste with the above valve. Usually takes about 3-5 minutes to get TDS down to 1-2. Then I switch the valve around to run the RO water through the DI. I haven't changed out DI in over a year.

 

[Xtc_link]

Co2 is present but at 3ppm I'm not sure if a degassing tower would be worth it. 212tds from tap 3tds after ro. I'm running a booster pump also it's at 84psi I think. It wasn't at 90 so I never fiddled with the adjustment

 

[Xtc_link]

I use a diverter valve that I picked up from BRS to run-to-waste the first couple of minutes of water on start up.

On start-up of my RO/DI unit, I get break through TDS of between 50-70. Instead of this burning up my DI, I run this to waste with the above valve. Usually takes about 3-5 minutes to get TDS down to 1-2. Then I switch the valve around to run the RO water through the DI. I haven't changed out DI in over a year.

I've debated going this route

 

[Jlobes]

I use a diverter valve that I picked up from BRS to run-to-waste the first couple of minutes of water on start up.

On start-up of my RO/DI unit, I get break through TDS of between 50-70. Instead of this burning up my DI, I run this to waste with the above valve. Usually takes about 3-5 minutes to get TDS down to 1-2. Then I switch the valve around to run the RO water through the DI. I haven't changed out DI in over a year.

seems handy and useful. easy fix as well.

 

[AZDesertRat]

It does not have to be an expensive 3 way valve. A simple 1/4" tee and ball valve works great and is a heck of a lot less than a 3 way. Point the tee down and install the valve on the low leg and water will take the path of least resistance.

 

[jason2459]

It does not have to be an expensive 3 way valve. A simple 1/4" tee and ball valve works great and is a heck of a lot less than a 3 way. Point the tee down and install the valve on the low leg and water will take the path of least resistance.

That's what I have setup and will run for a short bit before each use. Then flush the membranes for a bit longer after each use. I have a 300gpd unit so doesn't take more then a bit.


For the OP I use 3 DI stages. I posted about it recently so will copy paste what I posted as I have a hard time explaining it but basically what Randy said above with a 3rd stage added.

Copy/Paste in reference to RO/DI maintanence and when to change out the sediment and carbon cartridge:

Yep, I would change it out if it looks "soiled" and pressure drops. Around 8-10 months with my current water supply. Used to be sooner 4-6 months on my old water supply. I use a decent amount of water each month.

I switch out my carbon blocks every 6 months in months divisible by 6 which makes it easier for me to remember which would be June and December. I could wait a year like many or could use a chlorine test to know when better but this is easier for me and carbon stages are cheap and I don't trust public water supply to be consistent with how much chlorine they add.

I switch out my dual membranes on years divisible by 3 so I don't have to remember the last time I swapped them out. I did this in 2009, 2012, 2015, and will again in 2018. I also make sure to back flush the membranes after each use. There are automatic flushing kits but I never got around to getting one. If you don't maintain the membranes properly you'll probably have to change them out sooner. Watch the incoming and outgoing TDS and waste to RO water ratio will also let you know. Assuming you know what that ratio should be.

DI I swap through 3 stages of it. I get color changing but used to use the color change to know when to start checking the TDS. I would not change it out until I saw 1 on my TDS meter which was often after all the color has changed. Now as soon as I see 99% of the color changed I take that last stage with the newest DI resin (3rd stage) and put it into the stage before it (2nd stage). Take that 2nd stage's DI cartridge and put it into the stage before that which is the 1st stage. Then discard the oldest DI resin that was in the 1st stage that was replaced by the DI cartridge from the 2nd stage. I hope I explained that clear enough. This has saved me some DI resin quite a bit. Even if its registering 1 it's still reducing the TDS to at least that point and has some life left IMO.

So now I'm usually seeing a drop from 250ish going into my membranes to 9ish out. Then after my first DI stage 2ish, after my 2nd DI stage 1ish, and after the last DI stage 0.