It is my understanding that DI water at 18 megaohm is pure H2O. Can someone explain to me why when DI travels through cast iron pipe that it will cause the cast iron to leach into the fluid stream? Is the statement above even true? Is this statement true for all metal piping? ie., copper, stainless, sch. 40 steel? Is DI water safe for human consumption? I'm trying to understand the chemistry behind DI water.
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Deionized Water 2
- Thread starter promero
- Start date
promero,
Because deionized water is so pure, there is a strong driving force for minerals to be dissolved into it. This is especially true when the deionized water is slightly acidic. Stainless steel can withstand the corrosive effect of most demineralized waters. I don't think that drinking DI is a very good idea...I'm not too sure why, but I think it reaks havoc on the uptake of minerals of your cells.
Hope this helped.
Because deionized water is so pure, there is a strong driving force for minerals to be dissolved into it. This is especially true when the deionized water is slightly acidic. Stainless steel can withstand the corrosive effect of most demineralized waters. I don't think that drinking DI is a very good idea...I'm not too sure why, but I think it reaks havoc on the uptake of minerals of your cells.
Hope this helped.
DI water is highly corrosive at 18 mega-ohm. It will attack most metals including Stainless Steel. It is safe to the human skin, but if you wished to drink it I doubt it would taste very good.
From my experience, when plumbing DI water use 316L SS, which has been chemically protected (passivated). The chemical treatment will extend the life of the plumbing but not necessarily prevent it from corroding.
Because the water is pure (lacking ions), the natural process would be to accumulate ions, and this would be why you are observing leaching of the cast iron into water supply.
A corrosion engineer may be able to provide you with more details as to what is happening.
Hope this helps.
From my experience, when plumbing DI water use 316L SS, which has been chemically protected (passivated). The chemical treatment will extend the life of the plumbing but not necessarily prevent it from corroding.
Because the water is pure (lacking ions), the natural process would be to accumulate ions, and this would be why you are observing leaching of the cast iron into water supply.
A corrosion engineer may be able to provide you with more details as to what is happening.
Hope this helps.
DeltaCascade
Chemical
Yes, perhaps surprisingly, there is lots of chemistry with respect to demin water. It is not bufferred, so atmospheric CO2 candissolve into it, lowering pH. However, pH measurements have little meaning in high purity water, so if it doesn't read pH=7.0, dont be alarmed. Similarly, dissolved oxygen can enhance its corrosivity. For example, check out Langelier Saturation index for demin water, it is negative, indicating corrosivity. Resistance or conductivity is a good indicator of dissolved subtances, but not for dissolved oxygen, or suspended solids. Surprisingly, there may also be microbiological activity as slimes can grow in demin water tanks, often at the liquid level, and accelerated corrosion can occur beneath slime deposits, where the chemistry there is different (similarly in cracks and crannys on a metals surface).
Stainless steel pipes should be fine, but you may want deaerated (no dissolved oxygen) water for cast iron or even mild steel pipes ... mechanical or chemically deaerated, like in your typical boiler feed water system.
Stainless steel pipes should be fine, but you may want deaerated (no dissolved oxygen) water for cast iron or even mild steel pipes ... mechanical or chemically deaerated, like in your typical boiler feed water system.
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- #5
I think the corrosion has been covered quite well so far, and I can add from presonal experience that Demin water will corrode copper pipe, to the point where you will have measureable levels of copper in the water within hours.
As far as human consuption, DI WATER IS NOT SAFE TO DRINK! It is often call "slow death" by people in the water treatment industry. Drinking DI water on a regular basis will slowly rob the body of vital minerals, and death can occur. Now, if you drink a glass of DI water, you will not notice any adverse affects. But, it will not taste very good at all, because the water we are used to drinking actually has a small amount of flavor from the minerals it contains. In fact, if you read the labels on bottled water, you will find statments like this: "treatment by reverse osmosis, and enhanced with minerals for a pure, fresh taste."
As far as human consuption, DI WATER IS NOT SAFE TO DRINK! It is often call "slow death" by people in the water treatment industry. Drinking DI water on a regular basis will slowly rob the body of vital minerals, and death can occur. Now, if you drink a glass of DI water, you will not notice any adverse affects. But, it will not taste very good at all, because the water we are used to drinking actually has a small amount of flavor from the minerals it contains. In fact, if you read the labels on bottled water, you will find statments like this: "treatment by reverse osmosis, and enhanced with minerals for a pure, fresh taste."
DeltaCascade
Chemical
Demin water is not too far off from rain water, isn't it?
I'd guess that demin water would be bad for your health if you had a diet where your water intake accounted also for most all of your daily mineral intake.
If you drank only demin water, my guess is just eat well, even eat mud, to get them minerals, and you'd be fine.
I don't think it would harm you, if your overall dietary intake was healthy, unless you drowned in it (or like, drank a cubic meter in one sitting)
Just an opinion.
Cheers//
I'd guess that demin water would be bad for your health if you had a diet where your water intake accounted also for most all of your daily mineral intake.
If you drank only demin water, my guess is just eat well, even eat mud, to get them minerals, and you'd be fine.
I don't think it would harm you, if your overall dietary intake was healthy, unless you drowned in it (or like, drank a cubic meter in one sitting)
Just an opinion.
Cheers//
I'm not sure what would happen if you ate much more than the average amount of minerals outside of water intake. The thing is that demin water is very far from rain water, becuase it is very pure, with virtually no mineral content, and, because of that, it actually robs the body of minerals. So it's not just that it lacks minerals, it takes them from the body.
Check the label of many bottled waters, and you will see that they are indeed de-mineralized. Some by RO, some by IX, and then bottled. Some have minute minerals added back for taste, but some don't. I can't see how demin water could hurt you, unless material leached from the container into the water that was harmful, such as lead from solder, or monomers.
Many communities use RO sea water for drinking, including the military.
Just my opinion.
Many communities use RO sea water for drinking, including the military.
Just my opinion.
DeltaCascade
Chemical
More on corrosion, demin water can be used, for example, in closed water heating or cooling loops, like radiators on a car or diesel, in chemical plants, etc. One just must add corrosion inhibitors (eg: molybdate or nitrite or phosphate based inhibitors), which is easier than keeping dissolved oxygen out. In either case pH is usually also raised to about 8.5 or slightly higher (depending upon metallurgy) to reduce corrosivity. Demin water may be preferred in high temperature loops to prevent mineral scale and associated problems.
Cheers//
Cheers//
As a lot of people may know, the semiconductor industry uses vast amounts of 18 megaohm water. One wafer fab I think can use about 1 million gal/day. Purity is critical for their process and they use exclusively PVDF (polyvinylidene flouride) piping and PVDF lined fiberglass storage tanks. There are several manufacturers of the raw PVDF polymer (Atofina is the biggest, I think) and I know of a few manufacturers of piping and vessels.
PVDF is used primarily because there is virtually no leaching of trace minerals as you might get with different steels. Another reason is the water is specifically treated to remove dissolved oxygen and one of the last steps is ozination to prevent biofilm. Ozone is very corrosive in most systems, but the PVDF holds up very well.
Hope this helps.
PVDF is used primarily because there is virtually no leaching of trace minerals as you might get with different steels. Another reason is the water is specifically treated to remove dissolved oxygen and one of the last steps is ozination to prevent biofilm. Ozone is very corrosive in most systems, but the PVDF holds up very well.
Hope this helps.
I think we are speaking of two different water qualities. Sea Water that is processed through RO (brackish water) is not pure enough to leach any minerals from the body, and home RO units are also not high enough pressure to produce ultra-pure water. It seems that the problem is the term 'demin water'. My comment was in reference to using 18 megaohm for potable water in an industrial setting. This practice is not used in any demin plants I have personally seen. I work for a supplier of industrial water treatment systems, and any potable water tanks I have seen are filled with water upsteam of the demin or final pass RO units. This has more reasons than just the mineral-leaching effects of the demin water, of course, such as the cost of producing the higher purity water when perfectly good drinking water is available earlier in the process.
Drinking and cooking with exclusively 18 megaohm demineralized water is not a healthy idea (cooking with it leaches the minerals from the food as well). I did mention that death can occur, but that is obviously an extreme case where an individual may not be getting proper nutrition in the first place. Maybe I stressed the point too much, because, in scouring the net a bit, I find that the jury still seems to be out on the dangers of drinking water of higher purities as opposed to the impurities contained in some communities' water systems.
Your point about dissolved impurities from piping material is absolutely correct, 18 megaohm demin water will dissolve any such impurities. That is why 316SS piping is used in most cases to transport water of that purity, the water will "corrode" carbon steel pipe, as strange as that might sound.
Drinking and cooking with exclusively 18 megaohm demineralized water is not a healthy idea (cooking with it leaches the minerals from the food as well). I did mention that death can occur, but that is obviously an extreme case where an individual may not be getting proper nutrition in the first place. Maybe I stressed the point too much, because, in scouring the net a bit, I find that the jury still seems to be out on the dangers of drinking water of higher purities as opposed to the impurities contained in some communities' water systems.
Your point about dissolved impurities from piping material is absolutely correct, 18 megaohm demin water will dissolve any such impurities. That is why 316SS piping is used in most cases to transport water of that purity, the water will "corrode" carbon steel pipe, as strange as that might sound.
DeltaCascade
Chemical
Regarding the demin-potable water question:
Rainwater has negligible mineral content too, doesn't it? But then again, rain water isn't potable water, and demin water isnt potable water. And rectangle isnt (always) a square? So one must define their specifications which lead to these terms of potable, demin, 18-MOhm (that's fairly clear), etc.
For example, is demin water pathogen free or chlorinated? Not necessarily (it is common for slime deposits to actually grow in demin tanks .. amazing little bugs). Therefore, demin waer it is not striclty potable water.
Canadian potable water quality guidelines make reference to epidemiological evidence that hardness (Ca, Mg) in water may be inversely proportional to occurence of cardiovasular disease. We all appear to be in agreement on that. Maximum levels of about 200 ppm hardness are recommended to prevent pipe and equipment scaling. Actually, adjusting demin water for a neutral or slighlty negative LSI (Langelier Stability Index), by adding calcium and alkalinity, would minimize corrosion, negating need for stainless steel (how many potable water systems are made of $tainless $teel?). In short, why would one want to use demin water for potable water system?
If demin water was to be used as potable water, would it not be required to be chlorinated? If so, adding Cl2 gas or bleach would surely take demin water out of the potable water pH range of 6.5-8.5 pH units. Then you'd at least need to add lime and/or soda ash. There's the need for minerals, again. Also, as mentioned above, taste may very well improve, too.
Bottled water is another story ... not too sure about their sanitation requirements ... likely stricter than that discussed above.
All things come together?
Cheers.
Rainwater has negligible mineral content too, doesn't it? But then again, rain water isn't potable water, and demin water isnt potable water. And rectangle isnt (always) a square? So one must define their specifications which lead to these terms of potable, demin, 18-MOhm (that's fairly clear), etc.
For example, is demin water pathogen free or chlorinated? Not necessarily (it is common for slime deposits to actually grow in demin tanks .. amazing little bugs). Therefore, demin waer it is not striclty potable water.
Canadian potable water quality guidelines make reference to epidemiological evidence that hardness (Ca, Mg) in water may be inversely proportional to occurence of cardiovasular disease. We all appear to be in agreement on that. Maximum levels of about 200 ppm hardness are recommended to prevent pipe and equipment scaling. Actually, adjusting demin water for a neutral or slighlty negative LSI (Langelier Stability Index), by adding calcium and alkalinity, would minimize corrosion, negating need for stainless steel (how many potable water systems are made of $tainless $teel?). In short, why would one want to use demin water for potable water system?
If demin water was to be used as potable water, would it not be required to be chlorinated? If so, adding Cl2 gas or bleach would surely take demin water out of the potable water pH range of 6.5-8.5 pH units. Then you'd at least need to add lime and/or soda ash. There's the need for minerals, again. Also, as mentioned above, taste may very well improve, too.
Bottled water is another story ... not too sure about their sanitation requirements ... likely stricter than that discussed above.
All things come together?
Cheers.
Referring to messages by josephn16 & DeltaCascade, please note that we added minerals to pure water, produced from sea water through reverse osmosis, to result in potable waterof minimum 15 German degrees total hardness. The reason is that water without salts increases the risk for cardiovascular diseases, as we were told. These reverse osmosis plants were useful for islands not having water in their land.
Surprising to meet bottled water coming from reverse osmosis plants, since bottled water comes from high quality soil springs and undergoes some sterilization (e.g. by UV, etc) to keep acceptable quality for a year. Bottled RO water (with added salts) is thought to exist only where natural potable water is very scare.
Surprising to meet bottled water coming from reverse osmosis plants, since bottled water comes from high quality soil springs and undergoes some sterilization (e.g. by UV, etc) to keep acceptable quality for a year. Bottled RO water (with added salts) is thought to exist only where natural potable water is very scare.
DeltaCascade
Chemical
Many seem to trust "bottled water" ... without even knowing where it comes from. Some are from spring water (ground water), some just "any old" water treated by reverse osmosis.
Correct me if I'm wrong, (though my research has shown me otherwise in this case), but I believe that rain water is, in fact, potable. CO2 leaching from the atmosphere is negligible and fouling of the water usually occurs upon contact with a contaminated surface, basically due to organic materials, (rotting leaves and other bacterial growth media). In arid region lacking these organic contaminants, rainwater catchment is quite common and affective for potable water supply. Sediment need only be removed.
Hello,
Why not use plastic pipes if it is so corrosive?
It is dangerous to drink to much. As earlier said the water interfear with the K - Na synaphsis. All the salt in the cell wants to even out the "salt free" environment outside the cell, thus the cells "explodes"
Petroni
Why not use plastic pipes if it is so corrosive?
It is dangerous to drink to much. As earlier said the water interfear with the K - Na synaphsis. All the salt in the cell wants to even out the "salt free" environment outside the cell, thus the cells "explodes"
Petroni
Everybody agrees DI water is not potable. But rain water is potable. I have worked worked in tropical countries where rain water is the prime source for irrigation, drinking,generation of electricity. I think if we collect rain water in a clean plastic container and analyse it, it may have more or less the same mineral content as that of potable water.
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In many places around the world rain water is acidic mostly because of CO2 absorption. There are other gases connected with nitrogen and sulphur which add acidity and chemical reactions to pristine water. Anyway, rain water should receive additions of alkali to avoid corrosion of distribution piping.
This is generally done in the western world.
Besides, at the risk of being too exacting, I'd add that pure water is not totally deionized because it autoionizes by splitting into [H3O+] and [HO-]. At 25C the molar concentrations of both ions are 10^-7 (pH=7). On heating the pH drops as a result of more ionization. So, at 60C the pH drops to 6.5 and the concentrations more than double. The concentration of these ions at 60C are more than 9 times that at 0C. But, behold! Drops in pH don't mean that water becomes more acidic. Both ions appear in the same concentration keeping the water neutral.
Because of the increase in ions activities (aka concentrations) water resistivity drops with rising temperatures: the 18 megaohm.cm figure, given above by Promero, is at 25C, it drops to 4 megaohm.cm at 60C, and to about 2 megaohm.cm at 80C.
This is generally done in the western world.
Besides, at the risk of being too exacting, I'd add that pure water is not totally deionized because it autoionizes by splitting into [H3O+] and [HO-]. At 25C the molar concentrations of both ions are 10^-7 (pH=7). On heating the pH drops as a result of more ionization. So, at 60C the pH drops to 6.5 and the concentrations more than double. The concentration of these ions at 60C are more than 9 times that at 0C. But, behold! Drops in pH don't mean that water becomes more acidic. Both ions appear in the same concentration keeping the water neutral.
Because of the increase in ions activities (aka concentrations) water resistivity drops with rising temperatures: the 18 megaohm.cm figure, given above by Promero, is at 25C, it drops to 4 megaohm.cm at 60C, and to about 2 megaohm.cm at 80C.
Hey guys,
Wanted to know the difference between demin water and deionised waters and searched the previous posts and found your fascinating discussion. Can some one on these threads advise me whether deionised and demin waters are the same? If not, what is the difference?
Regards,
Guru
Wanted to know the difference between demin water and deionised waters and searched the previous posts and found your fascinating discussion. Can some one on these threads advise me whether deionised and demin waters are the same? If not, what is the difference?
Regards,
Guru
I can not speak to the mineral content of rain water, but, moisture in the air needs something to condense on -- so every drop of rain that falls from the sky has some foreign matter (a speck of dust, etc) in it (am I wrong on this?)... I would assume then, that it has some mineral content in it -- I would further assume that it will pick up traces of minerals from whatever it touches in a similar manner as DI would from its contaiment -- I would expect that "pure" rainwater would need to be tested to see if it is safe to drink as a single source of water...
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