Regular water contains minerals that overtime can cause the radiator passages to fill up or get clogged with a gel or wax like substances.
To flush or clean your radiator and get rid from it, use CALGON a household detergent, or any other detergent that is NON-Phosphate.
When the engine has cooled, drain all coolant, fill with mixture of CALGON and water.
Run engine until it reach operating temp, then run for additional 5 min at that temp.
Wait for engine to cool down, and drain coolant.
Best Coolant is Chevron or Texaco ELC (Extra Long Coolant Life).
Only buy Concentrate, then mix with DISTILLED water only, per manufacturer instructions, based on the climate zone you live in.
In most southern Florida, 40% coolant and 60% water is best for maximum cooling efficiency.
Regular water will cause the engine block to rust with the minerals that's in it.
P.S. Remember, what are completely acceptable for some, are condemned by others. Some folks have NASA standards in operating, caring and maintaining there equipment.