Amsoil recommends the use of tap or softened water if mixing ADCB (Amsoil Dominator Coolant Boost) in straight water applications.
Distilled or demineralized water should only be used if it is going to be mixed with at least a minimum of 35% coolant to 65% water ratio. The coolant is required to neutralize the aggressiveness of the mineral hungry water.
Passive surface films must be created to properly protect the soft metals in the cooling system. The passivation process requires heat and flow in the system using either glycol, and/or ADCB surfactant to effectively develop these surface films. ADCB will develop this protective layer with straight water at 1.5 ounce/ quart ratio, or with a water/ coolant combination with ADCB added at a 1 ounce/ quart ratio.
The key is to immediately run the vehicle once the radiator has been filled. Storing a new radiator, with only water, particularly distilled, and ADCB may allow for bacterial growth and/ or corrosion of the untreated surfaces, both of which may result in leaks, or damage to the radiator. Using distilled water will increase the radiator's susceptibility to damage as distilled water is not electrochemically balanced; it is stripped of impurities and therefore ionically hungry, which will cause it to attack soft metals more aggressively. Drinking, spring, or softened are the recommended water types for use in a radiator, particularly in racing applications.