TDS Rising in Top Off Container

[LV3]

I have an RODI unit that makes 0 TDS water. I use a 20 gallon glass aquarium as a top off container for a frag tank. Today I checked using a handheld TDS meter and found that the TDS of the top off container is .06 ppm and the brute storage can where the water is made is 0 ppm. The glass aquarium top off container takes a while to exhaust (2 weeks or so). Is what I'm seeing ions being pulled back into the 0 TDS water in the top off container while it sits there waiting to be used? Is that possible? Thanks.

 

[K. Steven]

Yes, remember RODI water is devoid of everything, so it acts as a magnet. Keep the container covered and it shouldn't be an issue. Also, the TDS you're reading is likely 6 ppm. Hobby-grade handheld TDS meters likely cannot read into the hundredths of a part per million.

 

[LV3]

Also, the TDS you're reading is likely 6 ppm. Hobby-grade handheld TDS meters likely cannot read into the thousandths of a part per million.

Thank you, I checked again and it is reading 6 and not .06 ppm.

 

[Agiron86]

Not sure if this related or not, but would elevated tds cause nitrates to elevate?

 

[Randy Holmes-Farley Verified Community Expert]

What sort of container?

Even carbon dioxide from the air can add 1-2 ppm TDS. A tiny bit of salty dust getting in will also boost it. I wouldn't worry about it too much, as long as it is not a metal container.

 

[Randy Holmes-Farley Verified Community Expert]

Not sure if this related or not, but would elevated tds cause nitrates to elevate?

Not sure what you mean. Nitrate is detectable by TDS, but 0 ppm RO/DI water is unlikely to be a substantial source no matter what you read in it later, relative tot he huge amount of N coming from foods each day.

 

[LV3]

What sort of container?

The main storage container where RODI water is made is a brute can. The top off container is a rimmed aqueon tank from Petco with the glass lid. I drilled 2 small holes in the lid for the lines for the ATO pump but the lid is relatively tight. It's not air tight by no means. My biggest concern was that the evaporation rate seems to be longer than I expected and the rise in TDS had me worried.

 

[Randy Holmes-Farley Verified Community Expert]

The main storage container where RODI water is made is a brute can. The top off container is a rimmed aqueon tank from Petco with the glass lid. I drilled 2 small holes in the lid for the lines for the ATO pump but the lid is relatively tight. It's not air tight by no means. My biggest concern was that the evaporation rate seems to be longer than I expected and the rise in TDS had me worried.

I expect it is no concern.

 

[Agiron86]

Not sure what you mean. Nitrate is detectable by TDS, but 0 ppm RO/DI water is unlikely to be a substantial source no matter what you read in it later, relative tot he huge amount of N coming from foods each day.

Do I leave my ato container uncovered, my mutates are high and I was wondering if introducing ato water that has tds’s would cause my nitrates to remain high

 

[K. Steven]

Do I leave my ato container uncovered, my mutates are high and I was wondering if introducing ato water that has tds’s would cause my nitrates to remain high

Leaving your ATO container uncovered will cause your RODI water to accumulate TDS, but your nitrate issue shouldn't be from your top-off water as long as your TDS is zero leaving the DI resin. If there is nitrate slipping past your DI and into your top-off water (in which case, you'll want to replace your DI resin), it is negligible to the amount of nitrogen you are feeding the tank on a daily basis.

 

[Randy Holmes-Farley Verified Community Expert]

Do I leave my ato container uncovered, my mutates are high and I was wondering if introducing ato water that has tds’s would cause my nitrates to remain high

I agree with the last post. Nitrate is not likely significant in top off water with rising TDS, and you add HUGE amounts of N every day via foods anyway. Even if it was 5 ppm nitrate in top off water, it is not significant.