RODI Water gains tds after sitting

[Rudyduck]

Hello!

Just a quick question… I like to always have some RODI water on hand for emergencies and to make water changes faster. I always have it sitting at 0 TDS and check it before and after. When I went to do a water change today the RODI water which had sat for a few weeks was 41 TDS. So I dumped it and starting again. Any ideas on why?

I use separate buckets for RODI, salt mixing, and waste.

Thanks!

 

[Tangdora]

TDS Creep

 

[Randy Holmes-Farley Verified Community Expert]

Tiny bits of salty dust from the air or dissolution of small solids on the container inside will account for that.

 

[Randy Holmes-Farley Verified Community Expert]

No need to dump it.

 

[bluemon]

I store my rodi outside and some pollen gets in as well, I just try to skim off the visible chunks and use it.

I have never measured my TDS of created RODI though

 

[Rudyduck]

No need to dump it.

So even though the tds has creeped up it’s still okay to use and create salt water from?

 

[bluemon]

So even though the tds has creeped up it’s still okay to use and create salt water from?

yea, as long as the RODI was stored properly (tight lid, fairly clean and inert container), TDS by itself doesn't really mean anything inherently. It just means there are a lot of dissolved solids in there, and in the process of being created, the RO portion would have gotten rid of any questionable dissolved soilds. as long as the storage was fine, the additional dissolved solids wouldn't harm the tank

 

[Randy Holmes-Farley Verified Community Expert]

So even though the tds has creeped up it’s still okay to use and create salt water from?

Yes. TDS is just a measure of saltiness, not an indication the water is bad. Seawater has a tds of tens of thousands of ppm tds. :)

 

[Subsea]

So even though the tds has creeped up it’s still okay to use and create salt water from?

When I maintained boiler water chemistry at 300MW power plant for Dow Chemical, after we drew a sample, if beaker was left uncovered, using a pH meter, you immediately saw pH drop as carbon dioxide readily dissolved in water. And at the same time on a volt meter, conductivity increased. TDS scale measures conductivity of the water.

 

[_chiefxr33f]

When I maintained boiler water chemistry at 300MW power plant for Dow Chemical, after we drew a sample, if beaker was left uncovered, using a pH meter, you immediately saw pH drop as carbon dioxide readily dissolved in water. And at the same time on a volt meter, conductivity increased. TDS scale measures conductivity of the water.

This!

 

[Rudyduck]

yea, as long as the RODI was stored properly (tight lid, fairly clean and inert container), TDS by itself doesn't really mean anything inherently. It just means there are a lot of dissolved solids in there, and in the process of being created, the RO portion would have gotten rid of any questionable dissolved soilds. as long as the storage was fine, the additional dissolved solids wouldn't harm the tank

Great, Thanks so much!

 

[bluemon]

This!

When I maintained boiler water chemistry at 300MW power plant for Dow Chemical, after we drew a sample, if beaker was left uncovered, using a pH meter, you immediately saw pH drop as carbon dioxide readily dissolved in water. And at the same time on a volt meter, conductivity increased. TDS scale measures conductivity of the water.

Isn't TDS technically just the amount of dissolved solids?

That can mean salts in many of our cases which WOULD measure the conductivity of water, but often times, there are dissolved solids that are not salts and not conductive. So i wouldn't really say that.

 

[Rudyduck]

Yes. TDS is just a measure of saltiness, not an indication the water is bad. Seawater has a tds of tens of thousands of ppm tds. :)

Thank you! Really appreciate the help.

 

[Randy Holmes-Farley Verified Community Expert]

Isn't TDS technically just the amount of dissolved solids?

That can mean salts in many of our cases which WOULD measure the conductivity of water, but often times, there are dissolved solids that are not salts and not conductive. So i wouldn't really say that.

Yes, tds is a misnomer. It only detects charged ions, not things like table sugar.

 

[bluemon]

Isn't TDS technically just the amount of dissolved solids?

That can mean salts in many of our cases which WOULD measure the conductivity of water, but often times, there are dissolved solids that are not salts and not conductive. So i wouldn't really say that.

Yes, tds is a misnomer. It only detects charged ions, not things like table sugar.

Learned something new. Thank you!

 

[_chiefxr33f]

Isn't TDS technically just the amount of dissolved solids?

That can mean salts in many of our cases which WOULD measure the conductivity of water, but often times, there are dissolved solids that are not salts and not conductive. So i wouldn't really say that.

The way that a TDS meter measures this is through conductivity between the probes. Therefore- dissolved solids that are not salt based are not measurable without greater means of examination. Simple TDS is measured off of the salt content in the minerals in the water. Low TDS = Low conductivity.