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Re: [APD] Storing large amounts of RO water & reconditioning RO water

Hi Scott,
  In environmental studies, we use TDS as "total dissolved solids" and it encompasses everything from suspended micro-sediments (silt/clay) all the way to dissolved cations and anions.  
  Is there a difference between a TDS meter and a conductivity meter, or are you using the terms interchangeably here?
  Cheers & Gig'Em,

"S. Hieber" <shieber at yahoo_com> wrote:
  TDS meters actually test conductivity and display a reading that is a mathematical correlative of microsiemens. You can get a conductivity meter and use your own conversion formula -- no one formula for converting conductivity to salts or metals of dissolved solids exists; diff ones are conrrect for diff situations. Basically, TDS meters are always wrong but close enough for the task at hand if you aren't too picky. ;-)


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----- Original Message ----
From: Gordon McLellan 
To: aquatic plants digest 
Sent: Friday, February 24, 2006 2:49:32 PM
Subject: Re: [APD] Storing large amounts of RO water & reconditioning RO water

On 2/24/06, Steve B wrote:
> Now, for my first question:
> With this RO unit, how do I store enough water to get ready for "the big transition" from my plastic-plants-and-goldfish to my live-plants-and-angelfish tank I envision? I have researched this problem and people mentioned that they store and condition their RO water in "large new trashcans." I have gone looking for trash cans, and they are all very flimsy and thin. Is it possible to store 55 gallons of water in one of these plastic trashbins?


I recommend "Rubbermaid Roughneck" trash barrels... they hold about 30
gal each, and are $10 at the local hardware store. I have a pair of
them connected by a piece of hose, and they hold the water quite well.
After the first 10-20 gal the barrels become very rigid.

I just use a basic power head to extract the water as needed.

I don't use them for collection of RO water, so I don't need any fancy
shutoffs or anything... they just collect rain water and brine water
from my drinking water filter, excess is directed to an overflow pipe.

> My second question (and a follow-up):
> How do I know my water is truly purified by my RO filter? I took an RO sample I bought from my LFS and an RO sample I made with my new filter to a 3rd party tester (another LFS-big-box (petco). The RO water from my LFS was 7.0 pH with 0 salinity (they couldnt test for hardness). The RO water I made was 8.0 pH with 0 salinity. I figure as long as all the salinity (sodium) is removed it is OK, and the pH difference could come from my area water supplier's notorious daily pH swings. If my pH is so alkaline (8.0) today, it could be 6.5 tomorrow.

It is my understanding of how RO filters work, they are incapable of
taking sodium out of solution, without considerable pressure (I think
the number is around 700+ psi), requiring massive stainless steel
membrane housings. Perhaps that is just to desalinate sea-water?

I use a conductivity tester, called a TDS meter to test my filter ...
TDS levels of 550+ go in, 20-30 come out when I lived in the city. 
Now that I have a private well, TDS levels of ~280 go in, 0-7 come
out. I believe TDS stands for total dissolved salts - it tests for
metallic and mineral salts (such as sodium, calcium, magnesium, etc)

I hope this info is useful to you,


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