tds readings

[jnm107]

I just set up an RO/DI unit that is working. My question is "What is the proper reading for RO water to be placed into my FOWLR tank? I understand that more particulates (the non-conductive type) may appear in the water without affecting my TDS readings. I get 147 on my tap and 047 out of fresh RO water. Is this ok? Is there a better way to do my testing? THANKS. JOHN

[dragon_slayer]

a properly working RO membrane should give you a TDS reading of less then 10ppm even at a relatively high input level, your input is IMO on the lower side and you should have considerably lower output TDS. could be your meter rather then the membrane tho.

and just to be sure, you have discarded the first 5 gallon of product water that came out of the unit correct? if not this would explain the high readings.

hth
kc

[Randy Holmes-Farley]

This article should help:

What is TDS?
http://www.reefkeeping.com/issues/2004-04/rhf/feature/index.htm

from it:


"

7. If you are using a TDS or conductivity meter to monitor the performance of an RO membrane, then the measured value should drop by at least a factor of 10 from the starting tap water. So, for example, if the tap water reads 231 ppm, then the RO water should be less than 23 ppm. In many cases, it will drop much more than that. Less of a drop than a factor of 10 indicates a problem with the RO membrane.

8. If you are using a TDS or conductivity meter to monitor the performance of an RO/DI system, then the measured value should drop to near zero. Maybe 0-1 ppm. Higher values indicate that something is not functioning properly, or that the DI resin is becoming saturated and needs replacement. However, that does not necessarily mean that 2 ppm water is not OK to use. But beware that it may begin to rise fairly sharply when the resin becomes saturated. Do not agonize over 1 ppm vs. zero ppm. While pure water has a TDS well below 1 ppm, uncertainties from carbon dioxide in the air (which gets into the water and ionizes to provide some conductivity) and the TDS meter itself may yield results of 1 or 2 ppm even from pure water.
"

[jnm107]

Thank you all for your responses. I just needed verification before I rerouted my system. Thanks again.

[Randy Holmes-Farley]

You're welcome. :)

Good luck!