Distilled water or "soft" water in radiator?

68keyblr

Dirt-Old 20+Year Member
Mar 17, 2003
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OK so which is better? I've always use distilled water, but I recently heard the lack of ions in distilled water ends up sucking the ions out of the metal and therefore "soft" water is better (water from a water softener system).

Which is better and why?
 
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That's technically right. Distilled can be ionically imbalanced, but it often can get close to balanced just from being mixed with E/G antifreeze (the coolant becomes a donor).

If running straight water, then it's more of a problem. In such a case, the soft water is best (it is ionically much more balanced, having had Na ions added back into it as I recall).

The bottom line is that none of it will probably ever matter. I use distilled water myself. Were I going to run straight water with some additives for lubrication and rust inhibition, I would probably be a little more anal about it.

MHO.
Good luck.
 
Distilled water has "nothing" in it whatsoever and is somewhat agressive as water is the "universal solvent". Limit it's use to your battery where it's acid only by design. You can also use water off your AC condensers which is the same thing other than maybe a little dirt.

Normal home Zeolite Softened water is "zero temporary hardness" replaces Calcium and Magnesium ions with Sodium making it somewhat corrosive to metal but only has "permanent hardness" that won't come out of solution during boiling or in a boiler which is what you want.

Given the choice of the two I would use Softened tap water in 50/50 mix with long life antifreeze which raises the boiling point and protects against corrosion.

Given the ultimate choice I have always used my personal tap water which is not "zero" softened but modestly hard under 6 grains = 102ppm (it is common to blend the softened water with raw water to achieve this level of final hardness)and mix it 50/50 with full strength antifreeze. I change one gallon of this mixture every 2 years to keep the additives fresh. When I was racing in the summer heat I used "Water Wetter" also which gets rid of the bubbles that form inside your engine at the hottest points by breaking down the surface tension of the water thus better cooling due to lack of air bubbles forming on the hot surface.

If you don't mind paying extra the suggested premix 50/50 is probably the best way to go as certainly they would be careful what water they use for the mix to assure continuity or at least add sequestering agents to keep ions in solution.

Okay so I worked in the water industry for 35 years...guilty. Hope I didn't overkill your simple question.
 
Wow, great information guys...Thanks! I think I may just get the 50/50 and be done with it.

The only reason I'm paying more attention to it is because when I tore down my engine I found the coolant passages were almost entirely clogged with white junk (probably calcium). The previous owner must have used Arizona hose water in the cooling system.

Thanks for the input!
 
Wow, great information guys...Thanks! I think I may just get the 50/50 and be done with it.

The only reason I'm paying more attention to it is because when I tore down my engine I found the coolant passages were almost entirely clogged with white junk (probably calcium). The previous owner must have used Arizona hose water in the cooling system.

Thanks for the input!

it may be a stop leak additive, it covers the internals in a white deposit also....