Another RO/DI question

dtapke · 08/08/2018, 08:42 AM

So, I've been using an aquatic life color changing mixed bed resin DI filter, and after running maybe 300 gallons through (post RO is 11 TDS) It's starting to creep up to 2TDS.

It seems, that i'm using mostly one of the two resins in the mixed bed filter, thats a seemingly well known fact of life. So what i'd like to do is buy another cheap mixed bed resin filter, run that till its becoming depleted, then fill each of the two with singular resins. One Cation, one Anion. What i'm seeing though is that most folks are running a three stage DI with a Cation, Anion, and a mixed bed.

My question: why run the mixed bed after the two singulars? should it not be at 0TDS after running through the two independent filters?

marcom12345 · 08/08/2018, 08:45 AM

My understanding is, is that's a last resort/polisher....

With the third mixed bed canister, you ensure everything is out and that 3rd one lasts quite a long time.

Sent from my LG-LS993 using Tapatalk

Opus123 · 08/08/2018, 10:10 AM

I would think about upgrading your RO membrane. I have 450 tds at the tap and my post RO is only 2. At 2 tds I can get around 2,200 gals of 0 tds water from a di cartridge. At 11 tds you are only looking at around 400 gals out of a di cartridge.

dtapke · 08/08/2018, 10:40 AM

WOW. I'm up around 460-470tds out of the tap, in the summer out of the RO i'll run as low as 6 and in the winter around 14 (I'm in Wisconsin). I'm sure adding a pump would help. I'm currently using an Ispring RCC7 off amazon, I use it for brewing, drinking water, and then the only thing getting DI is the tank. I've only got a 24g nano, so I don't use that much resin in the first place.

The system is only a year old... are those post RO numbers really that bad?

dtapke · 08/08/2018, 10:41 AM

I'll have to double check my post RO number when i get home, maybe change out the pre filters and give the membrane a good flushing.

Opus123 · 08/08/2018, 11:50 AM

No, the 11 isn't bad for 470 water, it is around 98%. I have a spectrapure 99%+ rejection rate membrane. Flushing your membrane won't help. If all you have is a 24gal nano then you are probably fine with just keeping your system as is. Adding 2 more DI cartridges will take a while to pay for themselves.

Uncle99 · 08/08/2018, 05:26 PM

I don't worry about TDS until it reaches 10.
Meter error, to small a sample, some dust, all leads to TDS.
Any four stage will produce TDS water a zero, more filters just a increased cost.
Always take measurement immediately after making RODI, and nit from a cup, but from the vat itself.

dtapke · 08/09/2018, 09:22 AM

RO-8tds last night, I was overdue for a pre-filter change, changed pre-filters and flushed the RO membrane, I'll check my TDS after a couple days of use and see if its gone down.

As far as adding a 3 stage DI, using those canisters like I am, its a matter of $25 per mixed bed filter, I've already got two, one seems to be half depleted (tds creeping from 0 to 2) so i replaced it with a new one, back to 0. once that one starts to creep, i'll get a third. take the two existing filter housings and buy some bulk cation, anion, and use the new one as the third stage.

my RO/DI is stored in a 35g tank from tractor supply. with it sitting full for a few weeks i still get 0 TDS out of it. when I refill the tank i check the TDS of the water going into it straight out of the DI, so when it bumped up to 2 i knew it was a DI issue, not a storage or meter issue.

interesting to hear you don't worry about tds until 10 though Uncle99, as I've heard that we should really be focusing on 0. at the same time, the DI to get it from 10 to 0 is pretty cheap so i guess its no big deal to focus on 0 for me. I could imagine if i were making 100's of gallons of water or something I may think otherwise!

Opus123 · 08/09/2018, 10:57 AM

Pre filters have no effect on TDS. Their only purpose is to protect the RO membrane and remove chemicals like chlorine. Flushing will also have no effect or very little. You really shouldn't let the tds get above 0 because you have no idea what is in that number. You could have a tds of 1, but what if that 1 is something that could kill your coral or fish.

dtapke · 08/09/2018, 01:42 PM

That's kind of been my thoughts Opus, especially here in semi-rural Wisconsin, you never know if its some sort of runoff from a CAFO or other farm chemicals. As a home brewer as well i usually feel ok with running the plain RO water which i also treat with a variety of chemicals to get my calcium and such where i want it for my beers, but don't feel that 0tds is as important with that as my tiny ecosystem.

Thanks all for the input!

08/08/2018, 08:42 AM	#1
dtapke Registered Member Join Date: May 2018 Posts: 105	Another RO/DI question So, I've been using an aquatic life color changing mixed bed resin DI filter, and after running maybe 300 gallons through (post RO is 11 TDS) It's starting to creep up to 2TDS. It seems, that i'm using mostly one of the two resins in the mixed bed filter, thats a seemingly well known fact of life. So what i'd like to do is buy another cheap mixed bed resin filter, run that till its becoming depleted, then fill each of the two with singular resins. One Cation, one Anion. What i'm seeing though is that most folks are running a three stage DI with a Cation, Anion, and a mixed bed. My question: why run the mixed bed after the two singulars? should it not be at 0TDS after running through the two independent filters?

08/08/2018, 08:45 AM	#2
marcom12345 Registered Member Join Date: Mar 2013 Location: Battle creek, Michigan Posts: 101	My understanding is, is that's a last resort/polisher.... With the third mixed bed canister, you ensure everything is out and that 3rd one lasts quite a long time. Sent from my LG-LS993 using Tapatalk

08/08/2018, 10:10 AM	#3
Opus123 Registered Member Join Date: Jul 2005 Location: North Texas Posts: 605	I would think about upgrading your RO membrane. I have 450 tds at the tap and my post RO is only 2. At 2 tds I can get around 2,200 gals of 0 tds water from a di cartridge. At 11 tds you are only looking at around 400 gals out of a di cartridge.

08/08/2018, 10:40 AM	#4
dtapke Registered Member Join Date: May 2018 Posts: 105	WOW. I'm up around 460-470tds out of the tap, in the summer out of the RO i'll run as low as 6 and in the winter around 14 (I'm in Wisconsin). I'm sure adding a pump would help. I'm currently using an Ispring RCC7 off amazon, I use it for brewing, drinking water, and then the only thing getting DI is the tank. I've only got a 24g nano, so I don't use that much resin in the first place. The system is only a year old... are those post RO numbers really that bad?

08/08/2018, 10:41 AM	#5
dtapke Registered Member Join Date: May 2018 Posts: 105	I'll have to double check my post RO number when i get home, maybe change out the pre filters and give the membrane a good flushing.

08/08/2018, 11:50 AM	#6
Opus123 Registered Member Join Date: Jul 2005 Location: North Texas Posts: 605	No, the 11 isn't bad for 470 water, it is around 98%. I have a spectrapure 99%+ rejection rate membrane. Flushing your membrane won't help. If all you have is a 24gal nano then you are probably fine with just keeping your system as is. Adding 2 more DI cartridges will take a while to pay for themselves.

08/08/2018, 05:26 PM	#7
Uncle99 Crab Free Zone Join Date: Sep 2017 Location: Ontario, Canada Posts: 2,906	I don't worry about TDS until it reaches 10. Meter error, to small a sample, some dust, all leads to TDS. Any four stage will produce TDS water a zero, more filters just a increased cost. Always take measurement immediately after making RODI, and nit from a cup, but from the vat itself.

08/09/2018, 09:22 AM	#8
dtapke Registered Member Join Date: May 2018 Posts: 105	RO-8tds last night, I was overdue for a pre-filter change, changed pre-filters and flushed the RO membrane, I'll check my TDS after a couple days of use and see if its gone down. As far as adding a 3 stage DI, using those canisters like I am, its a matter of $25 per mixed bed filter, I've already got two, one seems to be half depleted (tds creeping from 0 to 2) so i replaced it with a new one, back to 0. once that one starts to creep, i'll get a third. take the two existing filter housings and buy some bulk cation, anion, and use the new one as the third stage. my RO/DI is stored in a 35g tank from tractor supply. with it sitting full for a few weeks i still get 0 TDS out of it. when I refill the tank i check the TDS of the water going into it straight out of the DI, so when it bumped up to 2 i knew it was a DI issue, not a storage or meter issue. interesting to hear you don't worry about tds until 10 though Uncle99, as I've heard that we should really be focusing on 0. at the same time, the DI to get it from 10 to 0 is pretty cheap so i guess its no big deal to focus on 0 for me. I could imagine if i were making 100's of gallons of water or something I may think otherwise!

08/09/2018, 10:57 AM	#9
Opus123 Registered Member Join Date: Jul 2005 Location: North Texas Posts: 605	Pre filters have no effect on TDS. Their only purpose is to protect the RO membrane and remove chemicals like chlorine. Flushing will also have no effect or very little. You really shouldn't let the tds get above 0 because you have no idea what is in that number. You could have a tds of 1, but what if that 1 is something that could kill your coral or fish.

08/09/2018, 01:42 PM	#10
dtapke Registered Member Join Date: May 2018 Posts: 105	That's kind of been my thoughts Opus, especially here in semi-rural Wisconsin, you never know if its some sort of runoff from a CAFO or other farm chemicals. As a home brewer as well i usually feel ok with running the plain RO water which i also treat with a variety of chemicals to get my calcium and such where i want it for my beers, but don't feel that 0tds is as important with that as my tiny ecosystem. Thanks all for the input!