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The best bet for water cooling projects that will not get below 0°C is distilled water. You may also add a viscosity-reducing additive or water wetter. Follow the label directions for any additive. The normal dosage of water wetters is 2-3%. Note that if you have mixed metals present, you should have an anti-corrosion additive. Some water wetter products have anti-corrosion additives while others do not.

The fluid should be clear (color irrelevant). A cloudy appearance, visible particulates in the water, or a decrease in system performance warrant investigation. If the fluid gets cloudy or has stuff floating around in it, it is past time for replacement. If system performance is decreasing, check your radiator for dust build-up before changing your fluid.

If you wish to cool at temperatures below 0°C, the fluid of choice is a blend of methanol and water. Windshield washer fluid is a suitable blend, though some brands may include unnecessary and undesirable additives like detergents. A pure blend of 33% methanol and 67% water will work well to at least –20°C. Regardless of your material selection, think carefully about both the material’s heat transfer capabilities and the safety of its use. All materials used in a typical cooling system have chemical compounds that will attack them. Polymers (tubing, pump components, etc.) may tolerate very high concentrations of some chemicals, yet fail under weak concentrations of others. Direct contact or extended exposure to certain chemical vapors may pose health risks. If you’re not certain of what you’re doing, learn more before proceeding.

Stay tuned for the next article in our series when we discuss radiators and water blocks. Things are bound to get interesting as these two items tend to be the least understood and the most vehemently discussed.

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Editor: And be sure to check out Dave’s other recent reviews on the subject of water cooling. These are worth-while reads for just about everyone:

General Water Cooling Equipment and Performance Guide
Water Cooling Equip. and Performance Guide – Pumps

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