Water Softener Water vs. RO/DI Water

manishkasera · 01/07/2015, 08:04 PM

I have the RO/DI unit that have dual TDS meter on it to read for incoming water and also output water.
Recently I have added the whole house water softener system and output of that goes to my RO/DI unit. I noticed that the TDS reading for input water is also ZERO now. My question is that do I still need the RO/DI unit or I can use the water directly to make my saltwater for the aquarium.
If TDS readings are same for input and output water what is the logic to use the RO/DI unit?

Raul-7 · 01/07/2015, 08:08 PM

A water softener merely replace Ca and Mg ions with Na or K ions. It doesn't reduce TDS.

manishkasera · 01/07/2015, 08:16 PM

Get it. If my TDS meter is reading water out of Softener as Zero do I still need the RO/DI?

dartier · 01/07/2015, 08:30 PM

Well that depends. Does the water softener contain a filtering capability? Cause just removing the Ca and Mg, does nothing for the chlorine, phosphates, heavy metals, etc. Infact the Ca and Mg that water softeners remove, are something that would be OK for your tank, though RO/DI's remove them in any case.

If the TDS is truly 0, it does not sound like it is just a water softener.

If your TDS meter is installed like mine (BRS 6 stage), then it measures the TDS after the RO membrane, just before the DI stage, and calls that the input. That reading is after the water has already been treated by the RO stage.

Dennis

bertoni · 01/07/2015, 08:32 PM

The TDS out of the softener shouldn't be zero ppm. If you get such a reading, either the meter is not precise enough, miscalibrated, or broken. Delivering water at zero ppm TDS just can't be done in a real world scenario using house plumbing. I'd check what the RO/DI unit actually is reading.

disc1 · 01/07/2015, 09:37 PM

What kind of unit and where are you getting the 0 reading for input? On most commercial RODI units with a dual inline TDS meter, the IN side is between the membrane and the DI stage. It's not the incoming water, it's post RO water. That can often read 0ppm for very soft water, but that still doesn't really guarantee the water until you put it through deionization.

BrentH · 01/08/2015, 04:20 PM

I have a whole house water softener and carbon block on my home .... All it does or is supposed to do is remove the chlorine and chloramines along with ca and mg .... I figured it would prolong the life of my rodi? Plus my tap water tastes and feels nice without chlorine in it

my Tds before my rodi and after the softer is like 270 it lowers it maybe 60 ppm

DivingTheWorld · 01/08/2015, 04:54 PM

We also have a water softener with a carbon pre-filter. I've tested the water coming from the softener as well as directly from the city (we have one tap softener free for plants, pond, etc.). I find my TDS meter input readings the same whether directly from the city or through the pre-filter/softener.

Randy Holmes-Farley · 01/08/2015, 06:13 PM

I think the TDS meter is not working if tap reads 0 ppm TDS, before or after a water softener.

manishkasera · 01/09/2015, 10:10 AM

Dennis and David you guys are right. It's my ignorance, IN is actually after the Membrane and OUT is after the Resin. So IN is not showing the TDS quantity of my house water from softener as I thought which completely makes sense.
Thank you all for your help guys.

01/07/2015, 08:04 PM	#1
manishkasera Registered Member Join Date: Mar 2005 Location: Vaughan ON, Canada Posts: 148	Water Softener Water vs. RO/DI Water I have the RO/DI unit that have dual TDS meter on it to read for incoming water and also output water. Recently I have added the whole house water softener system and output of that goes to my RO/DI unit. I noticed that the TDS reading for input water is also ZERO now. My question is that do I still need the RO/DI unit or I can use the water directly to make my saltwater for the aquarium. If TDS readings are same for input and output water what is the logic to use the RO/DI unit?

01/07/2015, 08:30 PM	#4
dartier Registered Member Join Date: Aug 2012 Location: Brampton, ON, Canada Posts: 958	Well that depends. Does the water softener contain a filtering capability? Cause just removing the Ca and Mg, does nothing for the chlorine, phosphates, heavy metals, etc. Infact the Ca and Mg that water softeners remove, are something that would be OK for your tank, though RO/DI's remove them in any case. If the TDS is truly 0, it does not sound like it is just a water softener. If your TDS meter is installed like mine (BRS 6 stage), then it measures the TDS after the RO membrane, just before the DI stage, and calls that the input. That reading is after the water has already been treated by the RO stage. Dennis __________________ 560G Miracles tank in process making a DIY DyMiCo style filter (for 560G) Current Tank Info: 560G Miracles tank in progress, 80Frag Temporary Last edited by dartier; 01/07/2015 at 08:39 PM.

01/07/2015, 08:32 PM	#5
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	The TDS out of the softener shouldn't be zero ppm. If you get such a reading, either the meter is not precise enough, miscalibrated, or broken. Delivering water at zero ppm TDS just can't be done in a real world scenario using house plumbing. I'd check what the RO/DI unit actually is reading. __________________ Jonathan Bertoni

01/07/2015, 09:37 PM	#6
disc1 -RT * ln(k) Join Date: Sep 2010 Location: Little Rock Posts: 9,705	What kind of unit and where are you getting the 0 reading for input? On most commercial RODI units with a dual inline TDS meter, the IN side is between the membrane and the DI stage. It's not the incoming water, it's post RO water. That can often read 0ppm for very soft water, but that still doesn't really guarantee the water until you put it through deionization. __________________ David Current Tank: Undergoing reconstruction...

01/08/2015, 06:13 PM	#9
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	I think the TDS meter is not working if tap reads 0 ppm TDS, before or after a water softener. __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

01/07/2015, 08:08 PM	#2
Raul-7 Registered Member Join Date: Aug 2004 Location: Lomita, CA Posts: 891	A water softener merely replace Ca and Mg ions with Na or K ions. It doesn't reduce TDS.

01/07/2015, 08:16 PM	#3
manishkasera Registered Member Join Date: Mar 2005 Location: Vaughan ON, Canada Posts: 148	Get it. If my TDS meter is reading water out of Softener as Zero do I still need the RO/DI?

01/08/2015, 04:20 PM	#7
BrentH Registered Member Join Date: Dec 2005 Location: so cal Posts: 1,288	I have a whole house water softener and carbon block on my home .... All it does or is supposed to do is remove the chlorine and chloramines along with ca and mg .... I figured it would prolong the life of my rodi? Plus my tap water tastes and feels nice without chlorine in it my Tds before my rodi and after the softer is like 270 it lowers it maybe 60 ppm

01/08/2015, 04:54 PM	#8
DivingTheWorld Registered Member Join Date: Sep 2013 Location: San Ramon, CA Posts: 1,963	We also have a water softener with a carbon pre-filter. I've tested the water coming from the softener as well as directly from the city (we have one tap softener free for plants, pond, etc.). I find my TDS meter input readings the same whether directly from the city or through the pre-filter/softener.

01/09/2015, 10:10 AM	#10
manishkasera Registered Member Join Date: Mar 2005 Location: Vaughan ON, Canada Posts: 148	Dennis and David you guys are right. It's my ignorance, IN is actually after the Membrane and OUT is after the Resin. So IN is not showing the TDS quantity of my house water from softener as I thought which completely makes sense. Thank you all for your help guys. Last edited by manishkasera; 01/09/2015 at 10:23 AM.