Water in radiator rusty looking

[njk53]

We used a Prestone product with pure tap water that was a rust inhibitor and water pump lubricant that worked pretty good. Haven't been able to find it as of late, Prestone may have quit making it. All cooling systems believe it or not will have a small amount of electricity running through it so, you have a small amount of electrolysis taking place feeding on the engine block and causing the water to rust up. We have been using the Red Line product, Water Wetter as of late. It seems to work pretty well.