High TDS

[tacosricos]

So I'm getting readings of 15-20 TDS after my RO membrane, which is causing me to burn through my DI pretty fast (I like to replace it at or before 3). I replaced the pre-filters with a good set from BRS about two weeks ago, and went os far as to replace the membrane a few days back. The new one is a Dow Filmtec. I made sure to flush the membrane as per instructions as well. My line pressure is 85 psi going into the membrane. I'm using and inline TDS meter on the output of the membrane and post DI. My membrane is a 75gpd.

I've been considering adding a second canister of DI resin and rotating them out, as well as upgrading to a spectrapure membrane (Though I hate to throw away a perfectly good membrane).

Any recommendations?

 

[Randy Holmes-Farley Verified Community Expert]

How fast is the DI depleting?

Is it well water?

 

[tacosricos]

How fast is the DI depleting?

Is it well water?

Yes, it is well water. The last batch went up to 3 in less than 2 weeks if I recall. I had replaced the prefilters and resin at the same time. I have since replaced the RO membrane and I'm still getting reading post-membrane of 15-20. I replaced the resin in my DI canister this morning, but have yet to make any water.

Thinking back on it now, the resin I used for the refill-before-last was made up of the leftovers of opened bags that had been stored in ziplocs. I'm thinking that the resin had possibly gone bad, it was fairly old. We'll see how long this batch lasts.

Thanks for your response.

 

[Randy Holmes-Farley Verified Community Expert]

If it is well water, the problem may be CO2 in it, which does not show up all that much in TDS but does deplete the DI.

You can determine how much of an issue it might be using this calculator and some tests:

https://www.hamzasreef.com/Contents/Calculators/CO2DIDepletion.php

 

[tacosricos]

If it is well water, the problem may be CO2 in it, which does not show up all that much in TDS but does deplete the DI.

You can determine how much of an issue it might be using this calculator and some tests:

https://www.hamzasreef.com/Contents/Calculators/CO2DIDepletion.php

Thank you. So assuming CO2 were the problem, what would my options be to reduce/eliminate it?

 

[Randy Holmes-Farley Verified Community Expert]

Thank you. So assuming CO2 were the problem, what would my options be to reduce/eliminate it?

Degassing the water before the RO. Many people set up degassing reservoirs. Essentially aerating the water.

 

[Opus]

What is your tds going into the membrane? That will help us determine if it is working. Based on your current tds you are getting, your DI should make between 200 to 300 gallons of 0 tds water.

 

[tacosricos]

I don't have a reading pre-RO, I don't own a handheld meter.

It's been less than a week since I changed out the resin (BRS color changing) and I'm getting a reading of 1 off of my TDS meter. I think I have made about 40 gallons with it.

I'm looking into getting the stuff required to test for CO2 per Randy's suggestion.