Is RODI water safe to drink?

[Kenneth Hooper]

The dangers of dihydrogen monoxide

WIKI article:
A 1983 April Fools' Day edition of the Durand Express, a weekly newspaper in Durand, Michigan, reported that "dihydrogen oxide" had been found in the city's water pipes, and warned that it was fatal if inhaled, and could produce blistering vapors.[1] The first appearance of the parody on the Internet was attributed by the Pittsburgh Post-Gazette to the "Coalition to Ban Dihydrogen Monoxide",[2][3] a parody organization at UC Santa Cruz following on-campus postings and newsgroup discussions in 1990.[4]

This new version of the parody was created by housemates while attending the University of California, Santa Cruz in 1989–1990,[2][4][better source needed] revised by Craig Jackson in 1994,[2] and brought to widespread public attention in 1997 when Nathan Zohner, a 14-year-old student, gathered petitions to ban "DHMO" as the basis of his science project, titled "How Gullible Are We?"[5]

 

[Dkeller_nc]

"How Gullible Are We?"[5]

Apparently, the right answer is "extremely". You might have heard about the "raw" water trend - a fair number of folks with a woefully inadequate knowledge about waterborne diseases apparently think that drinking untreated water from the ground is a good idea:

What to know about the "raw water" trend

A new Silicon Valley craze could make people sick.

www.vox.com

 

[Otrips]

So there seems to bit of confusion here, and possibly as a result of me not going into sufficient explanation in my posts about water sterilization/sanitation.

As Randy noted, it turns out that bacteria can indeed grow in highly purified water if that water is stored in a manner that allows inoculation of bacteria and/or bacterial spores from the environment. This is despite the fact that the water when produced has virtually zero dissolved nutrients - either inorganic such as ammonia and/or nitrates, or organic in the form of dissolved organic compounds. There's a good bit of speculation in the scientific literature as to why this might be the case, and one logical explanation is that the water can adsorb very small amounts of nitrogenous compounds from the air.

However, note that isn't the same as saying that RODI water is better at bacterial growth promotion than tap or unpurified water. If you put highly purified water into a suitable container and sterilize it (with, for example, and autoclave), and the container is fully sealed, there will be zero bacteria in it - forever. Or at least until the container breaks down and loses its seal integrity.

The reason that tap water is safe to store for drinking purposes for at least a fairly short period of time at room temperature is because of the chlorine/chloramine content. Those sanitants will continue to kill and/or inhibit the growth of bacteria for multiple days. However, if you remove the chlorine/chloramine from the tap water with a carbon filter, it will grow bacteria quite well - often to the point of cloudiness after setting for several days at room temperature.

The above is the reason that RO/DI systems intended for drinking purposes have an filter on the end of the dispenser. In addition to providing a final filtration step, it also serves as a one-way valve that prevents airflow and its potential bacterial contamination from back-flowing into the system when the water flow is turned off. And when the system is setup, or is broken into to change filters, a sanitization chemical is used in the system to kill any bacteria that might've been introduced, and to remove any biofilms that may have grown in the system since it was last maintained.

I completely understand that bacteria will grow most anywhere there is water & air especially so when there is nothing to inhibit it's growth, rather a lack of an appropriate amount of sanitizer to kill it. How much air & bacteria enters a RO system when shutting it off using a valve at the end of the line?

I think the difference is we may all be looking at this from different angles. People filing jugs of RO water and leaving it sit out at room temperature for days before drinking, or someone drinking from whatever they use to store the water intended for their tank. VS's someone who opens up their RO valve, lets the old water run through the line & fills a gallon jug for the day. How likely would the amount and type of bacteria one might ingest in that situation be more harmful than what could be found from a less than ideal tap?


This thread has gone is so many directions, it's become somewhat confusing. From RO/DI water being "safe" or not, to drinking the waste water, to bacteria growing on the membrane.

I think we can all agree tap water may or may not be "safe" and depends entirely on the individual tap location. Generally bacteria is a rather minor concern of tap water due to sanitation. Especially compared to Lead and other organic and inorganic compounds which in certain locations has proven to be of high or unacceptable levels and is much harder to remove from a municipal water system. Much easier to chlorinate than replace the pipes.
An RO/DI system will remove most contaminates making it much more "safe" to drink and more trustworthy then from a random or unknown tap.

 

[topjimmy]

they say things in that paper that a normally educated person would not accept as plausible.

That's because they are more likely a political organization, not a health one.

 

[THillPSU]

Then y the heck do our fish and corals use it lol funny how it’s good for them

When you add the salt mix you are putting all the right stuff back in the water for the fish and corals.

 

[Dkeller_nc]

I completely understand that bacteria will grow most anywhere there is water & air especially so when there is nothing to inhibit it's growth, rather a lack of an appropriate amount of sanitizer to kill it. How much air & bacteria enters a RO system when shutting it off using a valve at the end of the line?

I think the difference is we may all be looking at this from different angles. People filing jugs of RO water and leaving it sit out at room temperature for days before drinking, or someone drinking from whatever they use to store the water intended for their tank. VS's someone who opens up their RO valve, lets the old water run through the line & fills a gallon jug for the day. How likely would the amount and type of bacteria one might ingest in that situation be more harmful than what could be found from a less than ideal tap?


This thread has gone is so many directions, it's become somewhat confusing. From RO/DI water being "safe" or not, to drinking the waste water, to bacteria growing on the membrane.

I think we can all agree tap water may or may not be "safe" and depends entirely on the individual tap location. Generally bacteria is a rather minor concern of tap water due to sanitation. Especially compared to Lead and other organic and inorganic compounds which in certain locations has proven to be of high or unacceptable levels and is much harder to remove from a municipal water system. Much easier to chlorinate than replace the pipes.
An RO/DI system will remove most contaminates making it much more "safe" to drink and more trustworthy then from a random or unknown tap.

Generally when one is speaking of systems intended to provide drinking water, it's a case of "better safe than sorry", so they almost always include a terminal filter, that when wetted, will not allow air or other contaminants to pass back into the system from the dispense point. How much air/bacteria will re-enter a typical hobbyist's system might be quite hard to quantify. I know in my own system the product water line definitely does drain when I shut the system off, and from a drinking water sanitation standpoint, that would not be viewed favorably.

The question about flushing is a good one and relevant to this thread. One of the aspects of bacterial contamination in water systems is that the organisms typically form a bio-film. This film then sheds viable organisms into the slipstream as the water flows past. This is one reason that when sanitizing a high-purity water system used for pharmaceutical manufacturing, one adds the sanitizing agent to the system, sets it to recirculate, and allows this to continue for several hours. That's specifically to allow the sanitizing agent a chance to diffuse through any biofilms present and kill all of the organisms that make up the film.

As a hobbyist, you can actually detect the presence of a biofilm in something like a brute trash can that one's storing RODI in. Over time, the surface will feel "slimy" compared to the plastic surface on the outside of the container. That's a biofilm.

By the way, on the subject of municipal water, it's worth stating that with the exception of actual criminality in the unfortunate case of Flint, Michigan, tap water is one of the most scrutinized products in the US. It's tested frequently, and monitored closely, and is easily one of the safest of consumer products. Food is scrutinized to a far, far lesser extent, and the quantity of heavy metals that one is exposed to in daily life are far higher from food and environmental sources than from water.

 

[tony'stank]

I lived in AZ for 9 years. In AZ middle to high end home all RO
units in the kitchen for drinking and cooking. Most also had whole house salt-based Water softeners. I am not aware of any health studies showing issues with this type of water processing.

 

[Rollman]

Wow, didn’t know. been drinking for months since I set up my mixing station. Tasted great, guess I’ll stop lol

 

[siggy]

Sorry if this was covered, Thanks @Dkeller_nc and others for all the interesting articles.

These systems are also regularly sterilized with peroxide-based sterilants to prevent the growth of biofilms.

Drinking fountains and Ice machines are very plentiful in the Auto factories, they require cleaning and to be sanitized on a regular basis or after plumbing repairs have been performed. This is rarely performed due to the enormous resources required to perform these tasks. Our plant was built in 1941. Due to old piping, funny tasting water and inadequate maintenance the union requested filters and carbon blocks on every fountain and Ice machine. During an inspection by a water authority it was discovered that the water was too clean and a bactria had formed in most of the machines. All the systems had to be flushed and sanitized......Pay now or later. BTW It was an orange jell like substance, Now we place the
carbon block at the spigot for filling coffee pots or WB's

 

[skyrne_isk]

Just to clarify further;
Waste water from your RO/RODI is called Black Water.
This is the rejected water from your RO membrane, or even after your DI filter/s.
This water is immensely full of all the heavy metals/dissolved solids you do not want in your tank, and is not suitable for drinking. I also recommend it not be used for watering food gardens such as tomato/lettuce etc whatever you grow. But that's just me.

It's fine to use it for watering your lawn or anything else ornamental if you like, as long as it doesn't affect/effect the plants adversely. YMMV

this whole line of conversation is hilarious to me. You do realize that what is coming out of the RO unit is just your tap that has been stripped down, right? Unless you drank literally nothing but RODI and had a bad diet, the only risk is a “mild” off chance of something happening bacterially on the output of the unit. The filtering process doesn’t toxify the incoming water....sheesh.

Does taste bad though, won’t deny that.

 

[SeaDweller]

Sorry folks, but drinking deionized water in and of itself will not hurt you in the slightest. The idea behind this is an inappropriate extrapolation from laboratory science. Extremely pure water has a large capacity to dissolve ions from various containers that it's put into, which is why if one puts 18.3 megaohm laboratory grade water into a glass vessel, the resistivity will quickly drop into the 0.5-1.0 megaohm range. That's partly from the adsorption of CO2 in the air, but also dissolution of sodium and silica from the vessel walls itself. And if you keep highly pure water in a 316 stainless steel system that's not "passivated", you will get corrosion of the steel walls as a very tiny amount of it dissolves into the water (this is called "rouging").

These effects have led some to inappropriately assume that highly purified water is "corrosive" and that it will remove minerals from your body as they dissolve into the water if you drink it. There is a rather serious logical problem with this assertion, which is that your stomach contains a massive amount of electrolytes compared to what is required to make highly pure water into "normal" water. It's true that if you only drank highly purified water and your food was deficient in minerals, then at some point you might develop a mineral deficiency. This is often cited as evidence that drinking highly purified water is "bad for you". What alarmist websites that espouse this dreck aren't telling you is that you would likely develop the same mineral deficiency regardless of whether you were drinking "normal" water or highly purified water. And for the average person in developed countries, the vast majority of your daily mineral intact is from food, not water.

However, there are several reasons not to drink water from your average hobbyist's RODI system, though it has nothing to do with the water that's produced being inherently bad for you. The first is taste - a lot of what we perceive to be "good tasting water" comes from the minerals that are in it. Highly purified water tends to taste "flat". This is why, btw, that bottled water companies use RODI systems to purify the municipal sources of water that they use, then add sodium, calcium and magnesium salts back into it before they bottle it. The second reason not to drink hobbyist-produced RODI water has to do with sterility. Municipal sources add chlorine/chloramine to water for a reason, and that's to prevent you from getting a bunch of live pseudomonas and escherichia (among other genuses) when you get a drink of water from the sink. In a hobbyist's RODI system, the carbon blocks remove the chlorine/chloramine, so the rest of the system downstream from the pretreatment stage can definitely grow several types of problematic bacteria that you wouldn't want to drink.

That's why RODI systems that are used for manufacturing beverage products have 2 additional controls in the system, which are UV sterilization and ultrafiltration. These systems are also regularly sterilized with peroxide-based sterilants to prevent the growth of biofilms.

Bottom line - if you want to use RODI in an application were it will be heated/boiled, there's no reason not to. But don't drink it straight from your RODI system without adding in some additional components to ensure its microbiological safety.

Exactly. You beat me to it.

 

[Greg P]

this whole line of conversation is hilarious to me. You do realize that what is coming out of the RO unit is just your tap that has been stripped down, right? Unless you drank literally nothing but RODI and had a bad diet, the only risk is a “mild” off chance of something happening bacterially on the output of the unit. The filtering process doesn’t toxify the incoming water....sheesh.

Does taste bad though, won’t deny that.

Why are you quoting me on this?

I'm not against drinking RO water, just DI water.
And I'm against drinking Black water from the unit.

 

[madweazl]

Why are you quoting me on this?

I'm not against drinking RO water, just DI water.
And I'm against drinking Black water from the unit.

How is the waste water considered black water? It's not even grey water.

 

[Dkeller_nc]

If anyone wants to calculate what's in their RODI wastewater for purposes of watering plants, washing clothes, etc..., it's relatively easy. Provided you have a hobbyist RODI system intended for use on residential tap water pressure, the restriction is generally designed to give you a 1:4 ratio of water to wastewater. That means that whatever ions were in your incoming water will increase in your wastewater by about 20%. Technically, it will be a bit less than that since no RO membrane is 100% efficient.

Note that this doesn't apply to highly efficient commercial systems that operate at 300 psig with descaling injection - those systems may have as much as a 9 to 1 product-to-waste ratio, so the outgoing waste water will be about 10 times the concentration of ions in the incoming water.

 

[Ditryin]

I was going to start a thread on R2R asking why chugging some RO water from my new RO/DI unit recently made me queasy but I guess it's because of bacteria. Bummer... I had used the logic that by not having to buy bottled water for us and the dogs anymore that savings would pay for the unit.

 

[robbyg]

this whole line of conversation is hilarious to me. You do realize that what is coming out of the RO unit is just your tap that has been stripped down, right? Unless you drank literally nothing but RODI and had a bad diet, the only risk is a “mild” off chance of something happening bacterially on the output of the unit. The filtering process doesn’t toxify the incoming water....sheesh.

Does taste bad though, won’t deny that.

Yes it is just your tap water that has been "stripped down". Drink and enjoy

 

[itskingston]

Sorry folks, but drinking deionized water in and of itself will not hurt you in the slightest. The idea behind this is an inappropriate extrapolation from laboratory science. Extremely pure water has a large capacity to dissolve ions from various containers that it's put into, which is why if one puts 18.3 megaohm laboratory grade water into a glass vessel, the resistivity will quickly drop into the 0.5-1.0 megaohm range. That's partly from the adsorption of CO2 in the air, but also dissolution of sodium and silica from the vessel walls itself. And if you keep highly pure water in a 316 stainless steel system that's not "passivated", you will get corrosion of the steel walls as a very tiny amount of it dissolves into the water (this is called "rouging").

These effects have led some to inappropriately assume that highly purified water is "corrosive" and that it will remove minerals from your body as they dissolve into the water if you drink it. There is a rather serious logical problem with this assertion, which is that your stomach contains a massive amount of electrolytes compared to what is required to make highly pure water into "normal" water. It's true that if you only drank highly purified water and your food was deficient in minerals, then at some point you might develop a mineral deficiency. This is often cited as evidence that drinking highly purified water is "bad for you". What alarmist websites that espouse this dreck aren't telling you is that you would likely develop the same mineral deficiency regardless of whether you were drinking "normal" water or highly purified water. And for the average person in developed countries, the vast majority of your daily mineral intact is from food, not water.

However, there are several reasons not to drink water from your average hobbyist's RODI system, though it has nothing to do with the water that's produced being inherently bad for you. The first is taste - a lot of what we perceive to be "good tasting water" comes from the minerals that are in it. Highly purified water tends to taste "flat". This is why, btw, that bottled water companies use RODI systems to purify the municipal sources of water that they use, then add sodium, calcium and magnesium salts back into it before they bottle it. The second reason not to drink hobbyist-produced RODI water has to do with sterility. Municipal sources add chlorine/chloramine to water for a reason, and that's to prevent you from getting a bunch of live pseudomonas and escherichia (among other genuses) when you get a drink of water from the sink. In a hobbyist's RODI system, the carbon blocks remove the chlorine/chloramine, so the rest of the system downstream from the pretreatment stage can definitely grow several types of problematic bacteria that you wouldn't want to drink.

That's why RODI systems that are used for manufacturing beverage products have 2 additional controls in the system, which are UV sterilization and ultrafiltration. These systems are also regularly sterilized with peroxide-based sterilants to prevent the growth of biofilms.

Bottom line - if you want to use RODI in an application were it will be heated/boiled, there's no reason not to. But don't drink it straight from your RODI system without adding in some additional components to ensure its microbiological safety.

One of if not the most informative posts I've ran across, checked your main points of argument and only a slight (minute) discrepancy (which leads into the arguments you made)

Thank you! Have definitely bookmarked

 

[Phildago]

I was under the impression that rodi water cannot grow bacteria due to the absence of electrolytes. We're you referring to reverse osmosis water growing bacteria or are there specific strains that can actually grow in rodi water?

 

[WallyB]

Generally when one is speaking of systems intended to provide drinking water, it's a case of "better safe than sorry", so they almost always include a terminal filter, that when wetted, will not allow air or other contaminants to pass back into the system from the dispense point. How much air/bacteria will re-enter a typical hobbyist's system might be quite hard to quantify. I know in my own system the product water line definitely does drain when I shut the system off, and from a drinking water sanitation standpoint, that would not be viewed favorably.

The question about flushing is a good one and relevant to this thread. One of the aspects of bacterial contamination in water systems is that the organisms typically form a bio-film. This film then sheds viable organisms into the slipstream as the water flows past. This is one reason that when sanitizing a high-purity water system used for pharmaceutical manufacturing, one adds the sanitizing agent to the system, sets it to recirculate, and allows this to continue for several hours. That's specifically to allow the sanitizing agent a chance to diffuse through any biofilms present and kill all of the organisms that make up the film.

As a hobbyist, you can actually detect the presence of a biofilm in something like a brute trash can that one's storing RODI in. Over time, the surface will feel "slimy" compared to the plastic surface on the outside of the container. That's a biofilm.

By the way, on the subject of municipal water, it's worth stating that with the exception of actual criminality in the unfortunate case of Flint, Michigan, tap water is one of the most scrutinized products in the US. It's tested frequently, and monitored closely, and is easily one of the safest of consumer products. Food is scrutinized to a far, far lesser extent, and the quantity of heavy metals that one is exposed to in daily life are far higher from food and environmental sources than from water.

The whole bacteria thing is good to know.

What perfect timing to get this knowledge.

I actually had/have two ro system in my house. One for Tanks and one for Drinking.
Last week the 10 year old Fish Tank RO system broke, and I thought why not simplify. I put a T connector off the house RO system and hooked it into my TANK system.
But this got me thinking. My Tank system fills 3 reservoires that have simple float valves, so the values touch the water in those Slimy film buckets.
That could reverse contaminate my Drinking water Tank.

I am going to buy and put back a separate Drinking system ASAP.

Or maybe skip it. Tap water might just be as safe (if not safer) since I am not the best at maintaining my Post RO lines, tank, etc.

 

[Phildago]

Not only should bacteria technically not be able to survive (maybe rare extremophiles can), but it would need to break the laws of physics in order to grow.

If anybody has any further information on this please let us know