whats the difference?
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  1. #1
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    Default whats the difference?

    G'day Froggers, what is the difference between distilled water and demineralised water? Can distilled water be mixed with coolant concentrate and used in the cooling system. I also have an aluminium radiator.

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    IMO, distilled water is more pure than demineralised, and is ok to mix with coolant concentrate.

    I note you are in WA. Based on very good first hand knowledge (from Mercedes Benz Germany testing our Perth water for use in the Transperth buses some 40 years ago when I was involved with the initial supply of those buses), our scheme water is among the very worst in the world for corrosion of aluminium parts in the cooling system, due to the types of minerals in the water. Explains why early aluminium head engines didn't last long here.

    Hence I am very careful about what I use in my engines to this day. To the extent that when I purchase demineralised water (usually in 4L containers) I make sure that it is from a supplier in Victoria or elsewhere, certainly not WA, my theory being that at least they started with a less corrosive water base. It would be one of the few products that I do not prefer to buy local.

    I haven't bought distilled water for a long time, I guess it is cheaper to "manufacture" demineralised water. Distilled water (from condensed steam) should be pure regardless of which water they used to start with.

    Cheers.
    2004 Scenic I 2.0 auto (Hers)
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    Demineralised or deionised water has been passed through ion exchange resins that remove the mineral ions dissolved in it. Think of calcium, sodium, and traces of metallic salts. It cannot remove organics, and so is usually filtered as well. It isn't completely purified, but further processing, eg osmosis, can make it suitable for even medical use.

    Distilled water is condensed steam from a still, and in theory is pure, but the still usually collects some mineral scale which can redissolve into the product.

    Contamination standards exist for laboratory and medical usages. I doubt if car-intended products conform to lab standards, and apart from extremely tiny amounts of organic material I doubt there is any difference in the two products. None ever quote standards on the label. Batteries and cooling systems only require the mineral content to be removed.
    Last edited by seasink; 18th December 2017 at 05:03 PM.
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    Thanks for the information Fordman. I will use the distilled water then. I can't find demineralised water around the local communities in any case. You have a fine mechanical heritage behind you. Shane

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    Thankyou for the explaining the process Seasink. I will take that as a yes on the distilled water then. Shane

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    Quote Originally Posted by SHANE51 View Post
    Thanks for the information Fordman. I will use the distilled water then. I can't find demineralised water around the local communities in any case. You have a fine mechanical heritage behind you. Shane
    Hmm - that's strange. Try reading the fine print on the label - I have in front of me a 2 litre David Gray's Distilled Water (the usual shelf item from Woolie's, etc) - fine print: "This water is purified by deionisation - the name DISTILLED WATER is not intended to describe the process of purification" - go figure. To me, that is demineralised water, not distilled, but there must be some sort of agreement which allows for the "false marketing"??

    That one is actually made in WA - so my wife must have bought that one for the iron. When I get the 4 litre containers (probably BigW) they are from Geelong, Victoria, my preference for engines.

    Cheers.
    2004 Scenic I 2.0 auto (Hers)
    2016 Ford Territory (His)
    2004 WRX (Sunday car)

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    I have always used deionised water in batteries and haven't been fussy with radiators, relying on the anti-corrosion coolant additives. My batteries have lasted well, and the only radiator I ever had recored was 35 years old.

    Obtaining genuine distilled water may be difficult. Even rainwater isn't totally pure, though I would use it in a battery if appropriately collected.

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