What condition must be met for water to be considered scale forming?

For water to be considered scale forming, it is essential for it to contain alkalinity levels that contribute to the precipitation of minerals, particularly calcium carbonate. When the alkalinity is above 40 mg/l, it indicates a higher concentration of carbonate ions in the water, which can lead to the potential for scale formation when conditions allow, such as when there is an increase in temperature or concentration of dissolved minerals.

A pH below 6.5 typically indicates more acidic conditions, which would not favor scaling but rather dissolution of mineral deposits. Heating water above 60 degrees Celsius can enhance the tendency for scaling because warmer water can hold less dissolved calcium carbonate. Turbidity relates to the clarity of water and is more indicative of particulate matter rather than mineral saturation levels necessary for scale formation. Thus, high alkalinity is a primary factor in determining the potential for scaling in water systems.