facboy

ok, here's a silly question:

is it better to use distilled water or tap water in the coolant?

some people say that distilled water is good, because it's de-ionised/demineralised or something. other people say it's bad, because it's de-ionised/demineralised, and so is 'aggressive'

so...who is right, and why?

Waterguy

Distilled/deionized is right. It will be pH buffered by the antifreeze additives and will not be "aggressive." I wouldn't run straight water either way, though.

Sam Lin

If you have it, distilled water is the best choice as it has nothing in it to react with anything, not even trace amounts.

Sam

M758

In Az we have hardwater. This means calcium deposits form on just about anything. Distilled water is best since there is nothing in it to build up in the coolant system. The water is there to cool. Nothing more. If there is nothing it it but pure water it is the best.

facboy

what do you mean 'straight water'? does that just mean water by itself (ie no additives)?

turbo944

That's what he's talking about. Yes, you want to have some coolant in there as well for the anti-corrosion and other properties it brings. If you live in a very warm climate, 25-30% coolant and 70-75% distilled water is fine. Water is a better heat transfer agent than coolant is. And if you can find some down there, get you a bottle of Redline Water Wetter or I think Royal Purple also makes one. They will help keep your temps down as well when running hard. They add more heat transfer ability to the water. I've used it and seen it work firsthand.

And listen to M758.....you want nothing in your water. Distilled is best. It's about 70 cents per gallon here in the US. Super cheap. Even cheaper than that "pure" drinking water....lol Water by itself is not aggressive. It is a solvent and will wear things over time (see the Grand Canyon), but those deposits just start growing on things and you'll end up seeing brown/white growth all over your water passages which are the deposits building up, similar to what you'd see in a household water heater that's several year old.

Sam Lin

Yes. You can get away with it on a race car, but on the street you'll want antifreeze both for lower freezing point and to prevent corrosion.

Sam

facboy

oic...well i wasn't planning on running without the additives anyway. basically this is an 'i want to top up my radiator' question

Danno

"Even cheaper than that "pure" drinking water...."

Avoid the "drinking water" bottles you find the stores and go straight for "distilled". If it doesn't say distilled, but rather "rocky mountain spring" or "drinking" water, it's just tap-water that's been packaged into bottles. The minerals, solids and colliforms count of tap water is tightly regulated and in many cases, you'll find that the non-distilled "drinking water" is worse than the water that comes out of the faucet tap.

FSAEracer03

May I suggest adding "water wetter" to a combo of 1 part coolant to 2-3 parts distilled water... very good results.

facboy

thanks guys! i've got 'demineralised water' from the service station, apparently for car batteries and irons (you know, for ironing shirts) and things? is this the right stuff?

KuHL 951

Yes, distilled water is always the best choice to use as a mixture base but never think that it will not corrode anything if used entirely by itself. De-ionized water is just what it says, unnatural, which makes it receptive to desolution of most minerals and active metals such as aluminum, zinc, and magnesium. Any water will try to reach equlibrium in regards to metal ion concentration with it's surrounding environment. Lacking any mineral or metal ions DI water will still react. I would never use straight DI water in a cooling system although it would have the best cooling properties YMMV; there should always be a corrosion inhibitor added especially in hi-temp, hi-velocity cooling systems. The main reason DI water is used in radiators is to mitigate scale buildup on cooling surfaces which block heat transfer.

Tap water should never be used unless you have your own glacier.

Off my box for now!

Jake951

I use tap water to water my house plants. The mineral deposits that build up around the sides of the flower pots are quite disgusting. I would never want that inside my engine. Go with distilled only.

turbo944

You caught my point exactly, Danno I have to laugh at a lot of the people who buy that stuff and think that it's really "pure".....

PorscheDoc

I've used slough water in a tractor trailer before Hey it got us home with a blown radiator hose.....thank god there is a slough about every mile in north dakota.