Lost in the world of RODI and TDS

[twilliard]

OK so I finaly got a TDS meter. I am working hard into finding out why I have 2PPM nitrates and 1.3 silicates from my RO. It is NEW, maybe 2 weeks old (6 stage RODI).

So I go and hook it up. It reads 111 PPM on the "in" and 6 PPM on the "out".
So what number does a person want to see as in TDS? Can it go to 0PPM?
Is my membrane crap?
What to do, oh what to do. Get a new one? IF so how does a person know a good membrane from a bad one?

 

[matts125]

with your tap water just over 100 ppm your RO should easily get that to 0 so I would say that something isnt working properly. what brand of RODI is it?

Matt

 

[twilliard]

It is made by Soumi Knight Systems

This is exactly the one I got

check it out

That is the link to it

 

[matts125]

I have never heard of that brand so I dont know about the quality..
I like the spectapure units my self..

Matt

 

[twilliard]

Ok so I understand this...

One brand of filter is better than the other when they all perform the same function?
Doesnt all RO membranes work with the same principle?

I guess I need to know if one membrane is better than the other. I can get a replacement membrane for this for under $35?? odd to me. Its a 5-10-carbon block-RO-DI-carbon system. RO being the heart of the system from what I have read.

 

[matts125]

yeah you mi9ght get better results with a new membrane...

Matt

 

[twilliard]

Thats kinda what I am thinking. I am actualy looking into a new one right now.
It states that it must be stored moist... I doubt it was. Makes sense to me.

Thanks Matt! Hope your tank is doing well!

 

[danno14]

RO info

RO membranes are measured as to the percentage of rejection. IE, the better (tested) Spectapure membranes are at least 98%. This means that if you start with 100ppm tap water, the RO will take it to 2ppm or less. The DI should take it to 0, but only if installed and flushed properly in the first place. Contact me offline for more tidbits.
Most of this is in the Spectrapure catalog
D

 

[twilliard]

Thanks a million!

 

[burning2nd]

i have as high as 140's in and ive never ever ever seen anything other then 0 ppm out.

 

[burning2nd]

also it say i can calibrate with something called
"NaCI"

whats that?

 

[chris&barb]

the membrane in that unit isnt a true RO membrane. it has a rejection rate of about 90%. i would swap that membrane for a Dow filmtec 75gpd membrane(dont forget to get the flow restrictor), its rejection rate is 98%.


most RO units over 75gpd dont use true RO membranes.

 

[chris&barb]

also it say i can calibrate with something called
"NaCI"

whats that?

sodium chloride = salt

http://en.wikipedia.org/wiki/Sodium_chloride

 

[Meche]

NaCI = Sodium, Carbon, and Iodine. Probably a typo, as I'm not sure this actually exists.

 

[twilliard]

the membrane in that unit isnt a true RO membrane. it has a rejection rate of about 90%. i would swap that membrane for a Dow filmtec 75gpd membrane(dont forget to get the flow restrictor), its rejection rate is 98%.


most RO units over 75gpd dont use true RO membranes.

Dang it I am done learning my lessons!
It is showing 106 IN and 6 OUT today
I will get a new membrane for it.

I am looking at getting a spectrapure unit just for my water room and leaving this one under the sink for drinking.

Thanks for the info chris

 

[danno14]

Huh?

"most RO units over 75gpd dont use true RO membranes"

Upon what is this statement based?

http://www.spectrapure.com/St_replac_psp_membranes.htm

http://www.spectrapure.com/St_replac_p3.htm

What's the difference, aside from volume capability?
Thx, D

 

[chris&barb]

"most RO units over 75gpd dont use true RO membranes"

Upon what is this statement based?

by reading the rejection rates of common RO units. most units under 75gpd have a rejection rate of 98% most over have a rate of 90%. the 90% units are not true RO units. you see i keep using the word "most". you can get true RO's over 75gpd but you have to check to be sure.

What's the difference, aside from volume capability?

an RO with 98% rejection will give you purer water. if you have a 98% unit and you starting water is 100ppm TDS your product water will be 2ppm TDS, with a 90% unit starting water 100ppmTDS your product water will be 10ppm TDS.

 

[danno14]

Taking offline. this won't be of any help to Scott

 

[DonW]

Dang it I am done learning my lessons!
It is showing 106 IN and 6 OUT today
I will get a new membrane for it.

I am looking at getting a spectrapure unit just for my water room and leaving this one under the sink for drinking.

Thanks for the info chris

Take a look at the filter guys. What TDS meter are you using? 150gpd units are probably the worst one made if your going to use them for this hobby, for drinking water they are fine.
To be blunt your di stage is also junk.

You need: One dow filmtech 75gpd membrane
One Flow restrictor rated for the new membrane
One Di add-on cartrige and resin
If you have good water pressure 60 psi at the membrane (check this with a gauge) not the inlet. You use a dual 75gpd membrane, also at the filter guys. This will really get that thing working and making alot of water with 0 TDS.

Again what tds meter are you using?

Don

 

[DonW]

If you look at the pic the two on the bottom right are what a good di filter looks like.