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Old 10-06-2020, 11:33   #1
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Mineral content of desalinated water

Recently I was reading that when cooking some foods in R.O. water, the minerals in the food leaches out leaving your food less nutritious. I have no idea if that is true or not but I started wondering just how "pure" desalinated water is and if there are trace minerals left behind after desalination. Are there any cruisers who have tested this?

Ironically, there are drops you can add to your drinking water to add trace minerals. These drops are made from sea water.
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Old 10-06-2020, 12:34   #2
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Re: Mineral content of desalinated water

Most use a tds meter (total dissolve solids). Household RO systems leave the water devoid of minerals. Seawater systems still leave some salt and mineral content.
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Old 10-06-2020, 15:50   #3
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Re: Mineral content of desalinated water

My RO unit give a TDS reading of around 200-250 ppm, sometimes less depending on where I am. RO removes all minerals and therefore will have health effects if you drink nothing but demineralised water. You can add salts back into the water to overcome this. Apparently it is also very aggressive to metal pipes and plumbing. Nobody likes angry water!
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Old 10-06-2020, 16:04   #4
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Re: Mineral content of desalinated water

No, no. Our desalinators are RO units, but not even close to what is considered an RO unit as far as water purity in their output.
A normal RO takes fresh drinking water and purifies it, often to what amounts to a TDS that is so low low it can’t be measured with consumer measuring devices.


Our watermakers take seawater and turn it into decent quality water that’s a little high on TDS compared to good drinking water, it’s quite a far stretch to what is normally consider as RO water used for example dialysis, which will measure 0 PPM TDS.

Still they are a miracle, they take in water at 35,000 ppm TDS and output say 250 PPM or so.
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Old 10-06-2020, 17:30   #5
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Re: Mineral content of desalinated water

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Originally Posted by a64pilot View Post
No, no. Our desalinators are RO units, but not even close to what is considered an RO unit as far as water purity in their output.
A normal RO takes fresh drinking water and purifies it, often to what amounts to a TDS that is so low low it can’t be measured with consumer measuring devices.


Our watermakers take seawater and turn it into decent quality water that’s a little high on TDS compared to good drinking water, it’s quite a far stretch to what is normally consider as RO water used for example dialysis, which will measure 0 PPM TDS.

Still they are a miracle, they take in water at 35,000 ppm TDS and output say 250 PPM or so.
What he said!
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Old 10-06-2020, 18:25   #6
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Re: Mineral content of desalinated water

I can tell you for certain, if you only drink RO water (desalinator) you could get sick. I'm speaking from experience, as I don't drink coffee, tea, alchohol, sodas or juice, as a rule. I lived on RO water for just over a year before feeling the effects.

We now use "remineralizing" cartridges in our water system, at least at the kitchen tap. It made all the difference.

Our new Spectra system makes water with a TDS of around 50ppm, I checked the bottle water we have here, and it shows 250ppm.

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Old 10-06-2020, 18:30   #7
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Re: Mineral content of desalinated water

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I can tell you for certain, if you only drink RO water (desalinator) you could get sick. I'm speaking from experience, as I don't drink coffee, tea, alchohol, sodas or juice, as a rule. I lived on RO water for just over a year before feeling the effects.

We now use "remineralizing" cartridges in our water system, at least at the kitchen tap. It made all the difference.

Our new Spectra system makes water with a TDS of around 50ppm, I checked the bottle water we have here, and it shows 250ppm.

Cheers.
Paul.

Agree. I usually add a pinch of salt to my diet.
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Old 10-06-2020, 18:32   #8
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Re: Mineral content of desalinated water

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Originally Posted by Sea Dreaming View Post
Recently I was reading that when cooking some foods in R.O. water, the minerals in the food leaches out leaving your food less nutritious. I have no idea if that is true or not but I started wondering just how "pure" desalinated water is and if there are trace minerals left behind after desalination. Are there any cruisers who have tested this?

Ironically, there are drops you can add to your drinking water to add trace minerals. These drops are made from sea water.
: )
A couple things here. First off there is NO scientific basis for high purity water “sucking the minerals” out of your food. NONE. This is one of those things that sounds all fancy and is dressed up with pseudoscience, but that is all it is.

I was an engineer for a major drug company, and we produced a lot of VERY high purity water. Somehow, the rumor got started among the workers on the factory floor that this high purity water would kill you if you drank it by exploding all your cells, or some such nonsense. Somehow, the rumor KEEP going even after I drank a liter of this water every day for a week.

Desalinated water runs from about 200 to 400 PPM TDS measured as Sodium chloride. This is higher salt content than a lot of city water systems that get their water from surface supplies, and lower than many than use well water.

Almost nobody gets much in the way of “trace” minerals from the water they drink anyway. Minerals come from food. Human beings can live just fine on 100% mineral free water. Rain water come pretty close, nobody dinking from a cistern ever suffered from “trace mineral deficiency” because they drank rain water.
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Old 10-06-2020, 19:10   #9
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Re: Mineral content of desalinated water

Grit said for certain that it made him sick. You don't think that that "hungry" water could leach the minerals out of a person's body?
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Old 10-06-2020, 19:34   #10
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Re: Mineral content of desalinated water

I don't know why people worry about such stuff. Eating a potato for example will give you more magnesium than you are going to get in your water. Swimming in the sea more salt.

Pretty hardly any minerals come from the water you drink. It's weird how some people jump on bandwagons and go off an write blog posts, and set about trying to convince others.
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Old 10-06-2020, 19:50   #11
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Re: Mineral content of desalinated water

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Grit said for certain that it made him sick. You don't think that that "hungry" water could leach the minerals out of a person's body?
He drank RO water for a year. Then he got sick. No causality is shown by this sequence of events, nor does his apparent recovery later after adding supplementary minerals. Unless he also stopped eating during that year, there were plenty of other mineral sources for his body... plenty!

Such anecdotal evidence is the source of many fables relative to diet and medicine.

The science ain't with him...

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Old 10-06-2020, 20:09   #12
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Re: Mineral content of desalinated water

https://www.corrosionpedia.com/defin...20of%20metals.
Supposedly it is corrosive. Might that be bad for us?
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Old 10-06-2020, 20:24   #13
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Re: Mineral content of desalinated water

a. There is science. I'm not sayin' right or wrong, since you can't tell people much about health, but here are two WHO studies.
https://apps.who.int/iris/bitstream/...556?sequence=1
https://www.who.int/water_sanitation...entschap12.pdf


The risk is stroke or heart attack, not general illness. The rates are very low, so a few anecdotal reports from sailors can't tell us anything one way or the other. The reports are based on large populations drinking desalinated water.


b. The concern is Ca and Mg, not NaCl. Because Ca and Mg are divalent, they are more easily removed than monovalent Na, down to levels as much as 30 times below WHO limits, even by yacht ROs.



Is it important? I don't know, but smart people seem to think it is and most RO water supplies follow this guidance.



And it turns out that good old hard spring water was "healthful" after all!



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Old 10-06-2020, 20:30   #14
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Re: Mineral content of desalinated water

But the issue at hand is desalinated water on a boat. The danger is that you are getting too much minerals not not enough. These guys are saying 250ppm TDS is acceptable. How much is too much?
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Old 10-06-2020, 20:33   #15
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Re: Mineral content of desalinated water

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But the issue at hand is desalinated water on a boat. The danger is that you are getting too much minerals not not enough. These guys are saying 250ppm TDS is acceptable. How much is too much?

No. It is not how many minerals, but which ones.


The EPA limit for TDS is 500 ppm (secondary standard--aesthetic effects). Any yacht RO that is operating correctly can meet this standard.
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