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Started by TJ 450, 25 July 2010, 10:12 AM


you dont need to goto a chemist, you can google it ;)


Practical example - in 1998 I (Sydney) bought a new kettle and my parents (Perth) coincidentally bought the same model.

I still use mine daily with tap water and it looks brand new, theirs was a mess after about 9 months.
1977 450SEL


Depends where you live in Perth.
In the hills the tap water comes from the Canning Dam but  on the plains it is bore water.



You don't need a chemist... but happens to be I'm in school, 4 years in, for biochemistry. The run down on it is something like this:

The distilled / deionized water contains no ions whatsoever. Therefore, no salt, calcium, potassium or any other ion or salt that would otherwise dissolve in water. It is pure H2O, 100%. If you were to take any quantity of it (say 1000 liters) and boil it, there would be absolutely no residue left behind when you boiled it all off. The same applies to vehicles. If you use, as we call it in the lab, DI water, it leaves no traces behind.

Here is the tricky part:

In the lab, it is commonplace to clean your utensils after doing reactions. You wouldn't want to leave things behind that could react unexpectedly in your next synthesis. So what do you do? Well, first we scrub them with a proper soap or solvent. Then we rinse them with.... distilled water. Why? Well, since DI water is nothing but water, it has a higher affinity to attract the salts and ions I mentioned earlier.

For example, if you have regular tap water and DI water, the tap water cannot hold as many ions because it already has some in there. This is like when you pour salt into water. It can only hold so much salt before the salt sinks to the bottom. Even boiling it, which increase the amount of dissolved ions it can hold, will only go so far.

So we use DI water because it will attract those things, doesn't have anything else in it, and rinses away to leave no residue. Then it is shaken to remove most water and set to air dry.

That said, I think probably you could cause problems going from tap to DI water, but I think it is far worse to just use tap water. In switching to DI water from tap, it is possible the water will pick up things that have collected on the internal surfaces of the cooling system because they will dissolve more readily. That said, I think this would be very, very minimal.

Then you must ask the question: how did those things get in the cooling system to begin with? From not using DI water. Although the system is closed and your loss of water should be minimal and probably not noticeable, the heating of the tap water can cause reactions that do not happen (or happen very slowly) at ambient temperature.

It is well known that heat generally will speed up a chemical reaction. Our engines get very hot, thus any contaminants will begin reacting very quickly with the internal surface of the cooling system to cause deposits. Any abrasions in the surface will speed this up. In the lab, when we want to cause something to crystallize or form a solid that is otherwise dissolved in a liquid, we will either add a small amount of the dry form of the chemical back to the one that is dissolved OR scratch the surface of the flask, to create a rough surface where the chemical can attach and begin crystallizing. Sometimes, this is fun to watch if the chemical crystallizes quickly (similar effect: see here). With the heating and cooling that goes on from running the car and turning it off, these will stay running through the system or (usually) begin depositing on the internal surfaces.

Your best bet is to use DI water for the cooling system. It is fine to drink, though some may think it has a more bitter taste than mineralized or spring water. Your body can accommodate for any leaching of ions that it does cause and we readily get most from our consumption of food. Although, there is a name for this. It is called water intoxication, otherwise known as hyper-hydration, which can cause hyponatremia--the acute loss of sodium through excretion.

The body of a health person can process about 15 liters of water per day. I don't remember the exact amount, but it takes quite a bit of water for one to drink to cause death. It is generally rare and usually only occurs in athletes who over consume it without electrolytes.

If you want to convert from tap to DI, I'd recommend doing a flush first. You can safely use vinegar, 50/50 with water is probably best. You can go with stronger acids, such as oxalic, muriatic, hydrochloric, etc, but you must keep in mind the composition of your radiator! Copper is safer but aluminum will react badly and you'll likely get holes with the stronger acids.

Even copper could get holes. Again, vinegar is safe for them all, but won't remove everything and needs to sit for a little while. Aside from that, I'd stick to something bought for the purpose as they know what concentrations are safe. If you get holes and followed instructions, you can always have them buy you a new radiator!

Bottom line: DI is best for the cooling system as it contains nothing but water.


One more note I forgot. I'm not sure about how they do things in AU and it probably differs between regions as it does it here, but... if your water is chlorinated you definitely shouldn't use it for a prolonged period of time. Chlorine is highly corrosive to aluminum, even in small quantities. Over time, it could create Aluminum Chloride (also called Aluminum Trichloride), which is a type of acid. There is a video of someone doing this reaction here, although I would never have chlorine gas in my room. Crazy! It is the white build up you see on aluminum, esp that exposed to the elements.

The other thing about tap water... each time you are adding water, you are adding more ions and replacing the water that evaporated. That means, over time, the amount of calcification that occurs will gradually increase because you're constantly adding new ions (which do not evaporate) and losing water (which does). Effect: build up.

Another reason not to use hydrochloric acid with aluminum: Chemical Reactions: Hydrochloric Acid + Aluminium Foil


our water is definitely chlorinated.

you can take water straight out of the tap and use a pool tester, as i have, and have results in the "ideal" section for chlorine level  ::)

TJ 450

Awesome response, thysonsacclaim! That's what I like to see. 8)

1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500


Quote from: thysonsacclaim on 09 August 2010, 03:14 AM
The other thing about tap water... each time you are adding water, you are adding more ions and replacing the water that evaporated.

So adding ions to an ion engine block is good yeah  ;D  Sounds like preventative maintenance. 
Don't answer that, lame joke I know.

I think I'm well overdue for a coolant system flush.  The paragraph that the quote was taken from typifies my 350's coolant system management I hate to admit.   There's always been something else to tinker with as problems pop up elsewhere and my coolant system's been neglected.  I shudder to think what calcified formations have grown in there.
1973 350SE, my first & fave


God this forum is great.
1977 450SEL


Quote from: flutes on 09 August 2010, 08:22 AM
God this forum is great.

You've only just come to that conclusion now ?  :o  ;D


Not convinced by thysonsacclaim's arguments for using distilled water, the logic seems a bit inconsistent.

You wash equipment in distilled water because it has no ions in it and it will collect any salts/ions on the walls of the equipment but recommend it for cooling systems because it doesn't leave deposits, ignoring its ability to suck out metallic ions from the cooling system metals.

Agree about Chlorine and pH, think I've seen mention of a recommended pH in MB books but don't know if pool test kits are any good for testing radiator water.

And I would think that if constantly evaporating Perth water in a kettle leaves a lot of material behind it would do the same in a cooling system - but only if it leaks and needs a regular supply of water.

Given what's in tap water and coolant, and the elevated temperatures involved I suspect the chemistry is more complicated than it appears.

I'm happy to keep using Melbourne's tap water.

koan, Defending myself in the face of superior knowledge...
Boogity, Boogity, Boogity, Amen!


Cool, I've learnt several things here, makes me wish I could have stayed at school. Who would have thought you could get into so much strife in your kitchen?


Let me clarify, because you bring up a good point that I didn't make clear before.

QuoteYou wash equipment in distilled water because it has no ions in it and it will collect any salts/ions on the walls of the equipment but recommend it for cooling systems because it doesn't leave deposits, ignoring its ability to suck out metallic ions from the cooling system metals.

Correct. It does attract ions better than tap water. But, it does not leech anything out of aluminum. However, water and aluminum react to form aluminum oxide as given by the following chemical reaction:

2Al + 3H2O > Al2O3 + 3H2 or
Aluminum + Water > Aluminum Oxide + Hydrogen Gas

Aluminum oxide is the other, very common white corrosion you will see on aluminum that has been exposed to the elements. It is very much like tarnish on silver or patina on copper as they are similar reactions. The outer coating on the metal protects it from further reactions. It is actually fairly inert in this state and usually takes an acid to remove it (same with copper---drop a green/tarnished copper coin in acid and see). This is provided, of course, that the water is neutral or slightly basic. In acidic conditions, this will change.

Here in Florida, for example, our water tends to have a lot of calcium in it because the ground is an old undersea environment. The average elevation here is only 30 meters above sea level, after all. Our highest elevation point is the lowest in the country and if you dig with a shovel, in less than a meter, you will start scooping up millions of tiny seashells, which are made of calcium. Dig a bit deeper and you can easily access the aquifer, where most of our water comes from. Because of this, I do not use 'my' tap water.

It is true that the chemistry is a little more involved than what it seems at first hand because there could be several things in tap water and coolant that cause various reactions. It gets very complex and to have any meaningful discussion would require actually taking samples and observing what happens.

On a final note, there is one thing we can all agree on. Distilled or deionized water is a scientific term that means a very specific thing (water with nothing else in it), whereas tap water is a vague, generalized term that has no real meaning in the realm of specifics. Some tap water is better than others and it depends where you live, etc.

I would say if you are comfortable with your water not being very hard, then go ahead and use it. If you have any questions about the relative hardness of your water, get a very, very clean stainless steel pot and boil a large quantity of water until there is nothing left. By doing this, you will be able to get a general idea of how hard your water is. If nothing is left, you should really be fine. The better way is to purchase a hard water test kit and test your water for hardness.

Can you get away with tap water? Yes. I think in most cases you might be fine, but it is important to know what could happen over long periods of time and to keep in mind how hard your water may be.

Edit: I found some information regarding aluminum and distilled water here. This is an article published in 1933 which details using a distiller for the creating of distilled water for lab purposes. If you read to the right of the photo, it states that aluminum has the property of being very suitable for this practice.

In addition, here is a table regarding how to store specific chemicals (ie in what composition container). It states:
QuoteWaters: vary in their action on aluminum. Distilled water regularly is stored and piped in aluminum equipment. High quality deionized water has no action on aluminum. Unpolluted rain water does not corrode aluminum. Fresh and salt waters in the pH range 4.5 - 8.5 cause only negligible attack of aluminum even at the boiling point, but certain of these waters cause pitting because they contain traces of heavy metal salts.


Wow thysonsacclaim, that should put koans fears aside  ;)

hi Tim, on a lighter note, check out this Youtube episode of FifthGear (Top gears poorer cousin), they fang a 190E against a Cosworth  :o

On the same page they buy a 800 pound Stirling Merc diesel and run it across England on Chip fry oil doing 70mph and no problems, cost them nothing for the fry oil, bloke was happy for them to take it away (Before the 'Healthy' comes around and sees it LOL).

Apparently Mr Diesel invented his high compression motor to run on Peanut Oil saying 'this would be advantageous to the agricultural sector as a low cost fuel' that WooHoo lasted until the Multi Nationals got on the band wagon  >:(

Thanks for you help on the weekend with the timing chain, looking forward to the first test drive next week all going well  :)

12/1979 450 SEL 148K on clock (museum piece)
12/1986 Lotus Esprit Turbo 87K on clock 'Darling, look what Q has brought for us, isn't it nice' :)


I hope so. The quoted material seems to support the fact that distilled AND probably tap water are fine. It actually says salt water won't corrode aluminum greatly, but you won't catch me putting that in my car anytime soon (there are things besides aluminum that it will come in contact with, anyway).

Point is, it seems that koan is right that tap water is probably okay as long as it doesn't have heavy metals. If it is drinking water, it shouldn't have these. It also seems the distilled water users are right as well. This should make everyone happy  ;D

Bottom line: if you haven't had any problems so far, do whatever you're doing because it is obviously working!

About Diesel:

It's a shame about the peanut oil. I did hear it was originally designed to run on peanut oil and later they toyed with the notion of soy and cottonseed oils. Also, before the outlawing of cannabis in the United States, there was research into using the oils from hemp (the non-psychoactive cousin to marijuana) for engine fuel and lubrication. I found that tidbit a few years ago researching lubricants and materials science. Too bad I can't put peanut oil into my 4.5  :'(

The unfortunate thing is that now, in many places in the US, they charge to have you take their oil because so many people were turning their old Merc diesels into biodiesel machines. Everyone jumped at $4.5 a gallon (3.78 liters) gasoline a few years ago... which is funny, because while our fuel prices certainly aren't the lowest in the world, they sure aren't the highest either. Not that I mind cheaper gas, though. $2.60 a gallon is fine by me.  ;D


Hi thysonsacclaim,

With all due respect to the USA we in Australia laughed when people on the news in the States complained about the high price of fuel when before the high oil prices we paid:

AU$4.16 an US gallon, then during the oil price hike it was $5.56 a US Gallon, bad news in anyone's language and certainly plenty of the fowl type when looking at the bowzer  :(

And the pollies kept saying 'we have relatively cheaper fuel than the rest of the world' yeah right  >:( i guess if you say that enough times you may just believe it  NOT :D

We had a lady from a waste cooking oil company come talk to us and they collect heaps and on sell to a fuel company called Gull who do a Bio Diesel ('up to 10% worth') my diesel work car did better fuel economy on that stuff  :)

The bloke from Merredin said waste cooking oil was not a problem in his town as most the Cockies had an old rattler to put it in (diesel merc) and you always know when your behind one  :P

Always interesting to hear of people research into cannabis when at Uni  :D

12/1979 450 SEL 148K on clock (museum piece)
12/1986 Lotus Esprit Turbo 87K on clock 'Darling, look what Q has brought for us, isn't it nice' :)