RO TDS 0 before DI Resin

[Sleepydoc]

So I started making a batch of RODI water this afternoon. After it had been running 30-45 minutes, I checked the TDS before and after the DI canisters. Normally the TDS of RO water in my system is 1-2 when it’s fully warmed up. Today it read 0!

So do I even need the DI resin? I figure I’ll keep it in line, just to sop up anything that might not be registering on the meter, but the DI resin ought to last me a while!

 

[Flippers4pups]

So I started making a batch of RODI water this afternoon. After it had been running 30-45 minutes, I checked the TDS before and after the DI canisters. Normally the TDS of RO water in my system is 1-2 when it’s fully warmed up. Today it read 0!

So do I even need the DI resin? I figure I’ll keep it in line, just to sop up anything that might not be registering on the meter, but the DI resin ought to last me a while!

I would continue to use it as it will remove what the carbon blocks don't get. Yes, your correct, the DI will last longer.

 

[Sleepydoc]

Yeah - that’s what I figured! I went back and checked later on an the TDS was back up to 1 after the RO membrane, so my resin has something to do.

My resin seems to deplete faster than I’d expect given the low TDS of my RO water; I’m thinking it may be due to excess CO2 in my water, but it’s not worth it for me to set up an aeration system to get rid of the CO2 before the DI canisters, so I’ll just replace it a bit more often.

 

[K7BMG]

I am on a well.
My RO/DI is fed directly from the well itself and does not go through the house soft water system,
as my water station is separate from the house.

My source water averages 20 ppm out of the ground.
4-5ppm between the RO and DI stages.
Between the Cation and Anion I average 45ppm and then always 0 after the mixed bed.

I go through a 10" canister of Anion every 250-300 gallons.

FYI

 

[LiveWire]

I would keep the DI. I am also on a well and my TDS is very low coming straight from the well to the RO system. It is so low that I have thought about just running my water through the 3 stage DI system as my Anion exhausts quickly due to my waters C02 levels as the well is 320 feet. My water has always been O coming out of the RO system but without the DI stages I know I would have high Co2 levels and low PH and possible other things making their way through. I plan to do some ICP testing in order to find out what exactly makes it past what and where throughout the RO/DI process.

 

[Sleepydoc]

I am on a well.
My RO/DI is fed directly from the well itself and does not go through the house soft water system,
as my water station is separate from the house.

My source water averages 20 ppm out of the ground.
4-5ppm between the RO and DI stages.
Between the Cation and Anion I average 45ppm and then always 0 after the mixed bed.

I go through a 10" canister of Anion every 250-300 gallons.

FYI

I'm curious as to how/why you are measuring higher ppm between your DI canisters than you have in your source water

 

[K7BMG]

I'm curious as to how/why you are measuring higher ppm between your DI canisters than you have in your source water

I was told by the BRS gang that's to be expected.

This was there explanation, as I understood it.
The Cation removes the charged ions leaving the negative ions for the Anion stage to handle, and the TDS meter can read the abundance of negatively charged ions between the stages.

So in a way the TDS meter verifies the Cation is working.
But I am not a chemist or scientist, I just have to take the information at face value and run with it.
I also don't know many who have a TDS probe installed between the two DI stages so its not common information.

 

[Opus]

I am on a well.
My RO/DI is fed directly from the well itself and does not go through the house soft water system,
as my water station is separate from the house.

My source water averages 20 ppm out of the ground.
4-5ppm between the RO and DI stages.
Between the Cation and Anion I average 45ppm and then always 0 after the mixed bed.

I go through a 10" canister of Anion every 250-300 gallons.

FYI

Shouldn't your tds after the RO be 0 or 1 at the most? At 4-5 it sounds like your RO membrane is not doing its job. My tap is 400 to 450 and after my RO membrane I'm at 3.

 

[K7BMG]

Shouldn't your tds after the RO be 0 or 1 at the most? At 4-5 it sounds like your RO membrane is not doing its job. My tap is 400 to 450 and after my RO membrane I'm at 3.

Since I have started this venture I have only produced about 700 gallons of water.
So I don't think my membranes should be exhausted. From what I remember so far I have always had readings at 4-5 after the RO stage.

I will know more about my source though as I have a second 3 stage TDS meter I plan on installing, one probe will be on the input or source. then a back up after the RO into the DI and then a back up on the final product.