Ro/di doest remove everything?

Cory · Jan 27, 2018

A member posted this is another thread:

https://www.hydroviv.com/blogs/water-smarts/tds-meters-and-testers

Would activated carbon remove pesticides?

Eric23 · Jan 27, 2018

Cory said:
A member posted this is another thread:

https://www.hydroviv.com/blogs/water-smarts/tds-meters-and-testers

Would activated carbon remove pesticides?

Ha Cory was just about to post in here asking the same thing you beat me to it !!!!

Big G · Jan 27, 2018

This product from BRS removes VOCs. Might want to email them: https://www.bulkreefsupply.com/brs-universal-carbon-block-filter-1-micron.html

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Randy Holmes-Farley · Jan 27, 2018

FWIW, the article says nothing about RO/DI and there is no concern for reefers.

I certainly agree that TDS is not a measure of pesticides and any other uncharged material.

But that, by no means, implies these things are ever in RO/DI water at levels that might be an issue. An RO membrane will very strongly reject large organic molecules such as pharmaceuticals and pesticides and many of them are charged and will be retined in a DI.. Much better rejection than for simple ions like sodium since they are all much bigger.

redfishbluefish · Jan 27, 2018

Cory said:
.......Would activated carbon remove pesticides?

Yes, between carbon and the RO membrane itself, you should be fine. EPA allows very low levels of pesticides in potable water.

EDIT TO ADD:

Found THIS for your reading enjoyment.

Eric23 · Jan 27, 2018

Randy Holmes-Farley said:
FWIW, the article says nothing about RO/DI and there is no concern for reefers.

I certainly agree that TDS is not a measure of pesticides and any other uncharged material.

But that, by no means, implies these things are ever in RO/DI water at levels that might be an issue. An RO membrane will very strongly reject large organic molecules such as pharmaceuticals and pesticides and many of them are charged and will be retined in a DI.. Much better rejection than for simple ions like sodium since they are all much bigger.

The way this came up was I was going through way to much di resin to fast and my tds meter which is after the DI was always reading 0 so I didn't bother changing the RO membrane. Months later and a lot of DI resin I'm having a hard time keeping coral alive and all of my parameters are good so I decided maybe it's my RO membrane and stuff is getting through the DI that my tds meter isn't reading and that's when I found that article. If your membrane goes bad and you star running through di resin really fast is there a chance things are getting into your tank even though the tds meter reads zero ?

Cory · Jan 27, 2018

The thing about that article that raised my eyebrow was this:

"Because TDS is an aggregate measure of charged compounds in water, uncharged things like motor oil, gasoline, many pharmaceuticals, and pesticides do not contribute to a TDS measurement. For example, the glass on the left in this article's header image contains deionized water with Malathion (an organophosphate pesticide) dissolved into it at 100 times higher concentration than allowed by the EPA for drinking water, and the TDS probe reads 000."

I guess its just a sales tactic and ro membranes would restrict these things?

Cory · Jan 27, 2018

Eric23 said:
The way this came up was I was going through way to much di resin to fast and my tds meter which is after the DI was always reading 0 so I didn't bother changing the RO membrane. Months later and a lot of DI resin I'm having a hard time keeping coral alive and all of my parameters are good so I decided maybe it's my RO membrane and stuff is getting through the DI that my tds meter isn't reading and that's when I found that article. If your membrane goes bad and you star running through di resin really fast is there a chance things are getting into your tank even though the tds meter reads zero ?

If your ro membrane stopped working and deion resin was left alone, according to that website oil, gas, pesticides would have gotten through if and thats if they were present.

Randy Holmes-Farley · Jan 27, 2018

Cory said:
The thing about that article that raised my eyebrow was this:

"Because TDS is an aggregate measure of charged compounds in water, uncharged things like motor oil, gasoline, many pharmaceuticals, and pesticides do not contribute to a TDS measurement. For example, the glass on the left in this article's header image contains deionized water with Malathion (an organophosphate pesticide) dissolved into it at 100 times higher concentration than allowed by the EPA for drinking water, and the TDS probe reads 000."

I guess its just a sales tactic and ro membranes would restrict these things?

They never say an RO/DI doesn't remove it that I could see. I say the same things in my "what is TDS" article

What Does a TDS Meter Actually Detect?

Since TDS meters are often used to test water "purity," it is important to understand what they do not detect. As conductivity meters in disguise, TDS meters will only detect mobile charged ions. They will not detect any neutral (uncharged) compounds. Such compounds include sugar, alcohol, many organics (including many pesticides and their residues), and unionized forms of silica, ammonia, and carbon dioxide. These meters also do not detect macroscopic particulates, as those are too large to move in the electric fields applied. So if you see "rusty" looking water from iron oxide particulates, that won't be measured. Neither will anything else that makes the water look cloudy. Bacteria and viruses also won't be detected.

Consequently, the term "total dissolved solids" is really quite a misnomer. "Total charged ions" is likely a much better term for what it measures. Fortunately, a measurement of total charged ions is good enough for many aquarium purposes.

Randy Holmes-Farley · Jan 27, 2018

Eric23 said:
The way this came up was I was going through way to much di resin to fast and my tds meter which is after the DI was always reading 0 so I didn't bother changing the RO membrane. Months later and a lot of DI resin I'm having a hard time keeping coral alive and all of my parameters are good so I decided maybe it's my RO membrane and stuff is getting through the DI that my tds meter isn't reading and that's when I found that article. If your membrane goes bad and you star running through di resin really fast is there a chance things are getting into your tank even though the tds meter reads zero ?

Most of the time, rapid DI depletion is due to CO2 in the source water, which is often true of well water.

I cannot rule out the possibility that something got through and that is the issue, but I think it is not the most likely explanation.

Lots of people have issues with corals, and often cannot determine what it is, but they are not typically RO/DI problems.

There are several different ways that most of these things are removed by an RO/DI (organics on the carbon block, for example), and seriously, hardly any of these are in EPA drinkable water to begin with at levels that would hurt a reef. Copper is by far the most likely coral killer in tap water, and most forms of it would be removed by a DI.

Randy Holmes-Farley · Jan 27, 2018

Cory said:
If your ro membrane stopped working and deion resin was left alone, according to that website oil, gas, pesticides would have gotten through if and thats if they were present.

My tap water is not filled with oil and gasoline, but maybe people in Texas have that issue.

Big G · Jan 27, 2018

Randy, there's about 800' of pvc pipe between my well and my RODI system. Anything for me to be concerned about as far as the PVC pipe leaching compounds into the water?

Cory · Jan 27, 2018

Randy Holmes-Farley said:
My tap water is not filled with oil and gasoline, but maybe people in Texas have that issue.

Lol. Ive seen a video on youtube where someone could light their tap water on fire due to h2s maybe.

Is a final carbon block a good idea?

Randy Holmes-Farley · Jan 27, 2018

Big G said:
Randy, there's about 800' of pvc pipe between my well and my RODI system. Anything for me to be concerned about as far as the PVC pipe leaching compounds into the water?

No, I don't think so. The organic compounds in PVC are reasonably large and hydrophobic and should be mostly taken out by the carbon and the RO membrane.