R/O Water Storage Question

[spawn]

When I make up my water I use 5 gal pails. 1 is a full time reservoir that never moves. The other 3 I use for mixing and water changes. When I'm finished a change I wash out & dry the pails thoroughly.
It seems that if I store water in these pails though for the course of the week there is is rise in the TDS from 000 up to 2-5, so I don't use it, so the question is :
Is this minimal rise in TDS because I must have missed a spot & if so is this water still safe to use because the rise would be due to some residual salt mix? I don't feel like wasting any more water.

[mike31154]

I use a rectangular rubbermaid type container to store & mix my fresh water, about 25 gals I think it holds. I just rinse it a little and let air dry between use. Have never checked the TDS of the RODI in there since I generally make it up a few days before water change and mix in the salt fairly quickly after production. There's quite a bit of calcium/mineral build up on the inside of the container after a few years of use, so I'm sure the TDS rises as soon as the RODI water hits it. I certainly wouldn't sweat a slight rise in TDS and definitely wouldn't discard it because of that. I used treated tap water for the first couple years of running my system, so a bit of TDS after RODI production is not going to get me too wound up. Do you have lids for your pails? That might keep the TDS down closer to 0 for you.

[spawn]

Yep there's lids on them whether there's water in them or if they're clean & dry. Also I forgot to mention that the water in the bucket I use for the reservoir has always had TDS of 000. & I do realize that I tend to over think most things.

[mike31154]

No worries, I have read other folks post that due to the very pure nature of RODI water, it has a tendency to be very aggressive in trying to absorb any kind of material it comes into contact with, including air, causing the TDS to naturally rise over a period of time. I'm just repeating info I have read in that regard, so no scientific evidence to back it up, but it does seem to make sense.

[spawn]

Thanks man, I've actually heard that before as well. Happy holidays.

[Myka]

What kind of buckets are these? I'm assuming they are old salt buckets, but maybe they aren't? I use a couple of food safe 65 gallon barrels for my water, and even after a month the water still has 0ppm TDS. I don't even use lids on them, just drape towels over them to keep dust out. I over-think everything too, and I'm super anal about things like RO/DI water, so in my case I would find your current situation unacceptable for fear of what exactly is that 5-10ppm anyway?? For the average reefer, probably not an issue.

[spawn]

They're food grade pails bought new from a plastics store here in the city. Not old salt pails. It was unacceptable to me as well that's why I didn't use it. However I don't like wasting all the water. So if the few ppm come after the 0tds water goes from my res into the mixing pails, it has to be some kind of residual from my mixing & obviously not perfect cleaning. So I'm not going to worry about it anymore, as long as the water coming out of the R/O Di. reads 000TDS.

[Phoenix_M]

Hi all,

new here, but saw this and thought i'd give you some insight.
you're probably experiencing carbon dioxide dissolving in the water. yup it does. this also alters the pH of the water very slightly too.
carbon dioxide and pH are closely linked; and works similarly to your blood. it's a 'buffer' system, and as pH changes, so does the amount of dissolved carbon dioxide, etc. it's in a balance. in your blood, actually, the change clicks your heart/lungs to race faster when there's higher c02 dissoloved.

essentially if you want to knwo more, look into the buffer equation for carbonate buffer systems. something like:

H2C03 <--> HC03(-) + H(+) <--> C03(2-) + 2H(+)
notice the left side has NO H+, the right side has 2 of them (the more "H+" you have, the higher the pH

there's your science.

-m

[spawn]

Does that mean that the water is safe to use? Kinda like I already kinda determined I was going to do?

[Phoenix_M]

yeah i'd say it's fair to use; UNLESS of course there's something leaching out of some contaminated plastic that you might be aware of.

we run a lab here and have a water polisher going 24/7..our water NEVER gets to absolutely "0" TDS due to c02 in atmosphere. it's nearly impossible.

guess a summary is; this is natural for very pure RO as Mike said.