Christopher McCann wrote:
>  Since water is different everywhere, pH and mineral wise, I can't see how 
> that argument works.
>  
>  Oh yeah, he also said (and we all agreed) that the pH of distilled water is 
> acidic and that is bad. I argued that with distilled water, you have a known 
> starting point and can formulate the coolant accordingly.
>   

I think in most municipal water systems the tap water is slightly basic,
to reduce corrosion in pipes.  Federal regulations require a range of
6.5 to 8.5, IIRC.

Once upon a time, VW blamed hard tap water in the U.S. for head
corrosion problems and head gasket leaks on Vanagons, and recommended
that only distilled water be used with their special coolant.  I have my
doubts, though.  I tend to think the corrosion was secondary -- the head
gaskets would start weeping and this would lead to corrosion of the head
sealing surface and a bigger leak.


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