Question about RODI water

Nhjmc · Jun 15, 2020

Good Morning! So wanted to see what others thought about this.....
Is it possible to get different TDS readings from the same batch of water?.....yesterday I purchased 30 gallons of "RODI water" (unsalted) from a LFS (not so local though it's an hour drive each way from my house). I watched the store employee fill the jugs out of a big brute holding container and saw the five stage RODI unit mounted on wall assuming their filters need to be changed.

I had 5 - 4.4 gallon jugs filled.....got home tested with TDS meter and was pretty shocked how high the readings were. And that each jug had a different TDS level/reading the highest being 052! Other jugs I tested the TDS read: 040, 031, 030, and one jug was 005. I tested each jug (sample of) three times. I know battery can't be bad in tester as it's not even 6 months old but did pick up a new/replacement battery.

I want to be certain before I contact the pet/fish store. Pretty annoyed about it as it's useless to me and did cost me $, over 2 hours & wear and tear on my car when I could of drove two min. from my house and purchased Rite Aid purified water by RO (which consistently has TDS readings of 002 - 003) not to mention I could of put that worse than tap water into my tank!
Thanks all!

chipmunkofdoom2 · Jun 15, 2020

If the water all came from the same Brute trashcan, it's unlikely that the conductivity reading varied that much between the containers. The TDS in deionized water can appear to rise over time, but that's mostly due to carbonic acid forming after the water absorbs CO2 from the air.

Contaminates in the water can also raise the TDS reading. That much of a change combined with the different readings leads me to believe that there was a reside in the cans.

Nhjmc · Jun 15, 2020

Hi! OK thank you. yeah I mean the store had quite the set up huge brute containers and also the huge white 55 gal plastic drums. The containers I used/refilled were empty "Nutri Seawater" jugs that were totally empty and had been sitting in trunk of my car for a few weeks. So do you think the readings from TDS meter are not accurate/am I safe to use the water?

dadnjesse · Jun 15, 2020

If you watched the employee fill the jugs from the same container, than they should all read the same other than what contaminants were in your jugs.

Uncle99 · Jun 15, 2020

Maybe the count includes some residue inside your jugs.
It would only take a few grains of salt (or else) to show those type readings.
TDS is not only just things we don’t want but some we do.
Say the count comes from some dry salt in the container, this would not be bad to add.
I’d use it.