[peon2t]

Well I don't know how it is in Australia but the tap water in Switzerland is very clean (you can drink it without any problems) so the main problem would be the chalk. But this probably isn't a big issue if you only put in such a small amount.

Plus: As I said eralier I found many sources on the web that strongly advise against the use of distilled water because it is (as they say) more corrosive to aluminium parts (and as far as I know much of the i30 diesel motor consists of aluminium).

Of course I can't tell what of it is true.

[Asterix]

Here in DK we also use tapwater without problems.

There must be something wrong with that Australian tap Water..

[Phil №❶]

We have the worst water in Australia where I live. Most capital cities have a nice river , good catchments etc, but South Australia is the driest state in the driest continent in the world. We have small catchments and our water is sourced in dry years from the river Murray, and we are at the end of the river, so large amounts of water are retained (by other states)  for irrigation, which reduces the flow, some years to zero. Consequently, the river salinity increases to such levels that plants die.

Distilled water is de-ionised, so that should be inert to aluminium. It takes ions to allow electricity to flow in an engine which causes corrosion. High voltage insulators are sprayed with distilled water to keep them clean, so it works.

[peon2t]

I did some more 'research' on this topic and it gets even more complicated.

- REAL distilled water is non-corrosive. But in the vast majority of cases you only get 'distillate-alike' water (probably I invented this term but I found no translation for the German word 'destillatgleich').

- 'distillate-alike' water CAN be more corrosive to aluminium but it isn't in every case. It depends on the way it has been produced. Today the methods that make 'agressive' water aren't the standard any more.

- If you don't fill in fresh tap-water on a regular basis you shouldn't expect any problems with chalk. Of course it's another story if your cooling circuit isn't as closed as it should be so that you have to refill often. Then you should consider to fill in 'real' coolant (but only the one that already is in the system because there are different kinds of collants that can react nasty if put in the same system) - and of course find out why you lost it in the first place.


By the way: Today I did a bit more than one hour of driving. Now the engine is cool again and I didn't lose any coolant. So at least my 'leakage' doen't seem to be acute. Maybe it was really just some air from the filling that vanished out of the cooling circuit recently. I found a thread in a German Hyundai board with a very long thread regarding this topic. Obviously there are quite some people affected by myterious coolant leakage.

[Phil №❶]

True distilled water is made from steam condensate, which is abundant at power stations and why they use it for cleaning high voltage insulators. The other stuff is very highly filtered water, but NOT de-ionised and therefore, still able to perform galvanic conduction of dissimilar metals. 

[rustynutz]

I believe Hyundai recommend distilled or demineralised water.....