Question regarding TDS

[JMo]

Hello,

I have a question regarding TDS. When making R/O water, should I try to achieve a TDS of 0 using DI resin. From what I can find online most R/O membrane only remove 96-99% TDS therefore the final output of TDS will be anywhere from 3-6 TDS. Is it acceptable to have a 96-99% rejection rate with a TDS of 3-6 without using DI resin. 

Edited May 20, 2023 by JMo

[jayc]

Hi @JMo

welcome to the forum.

You should try to achieve TDS of 0, and it is possible. it depends on your RO Filter, which might have more than just the resin filter. Mine, for example, is a 3 stage RO filter, that produces 0 TDS RO water (when the filters are new).

It can also depend on the tap water. If the source water was really high in TDS to start with, the filter might not be able to remove it all.

 

1 hour ago, JMo said:

Is it acceptable to have a 96-99% rejection rate with a TDS of 3-6 without using DI resin. 

I would only use this in a pinch and for short term since adding TDS to the tank will eventually cause an imbalance overtime. 

[JMo]

Thanks for the reply. Forgot to mention that this will be for a Caridina shrimp tank.  I may have to change the RO membrane and see if that help with the TDS. 

[jayc]

4 minutes ago, JMo said:

I may have to change the RO membrane and see if that help with the TDS. 

Definitely. Old RO membrane will let some TDS through. 

What TDS do you get out of the Tap?

[JMo]

Tap water TDS is 235 after some calculation it seems that I am getting a 97% rejection rate which is not to bad. 

I'm getting 6 TDS for my RO unit which is leading me to believe that it could be from the RO membrane though I am running dual RO membrane to help the RO to waste water ratio and dual sediment filters which might be overkill haha. 

Edited May 20, 2023 by JMo