Not just Water.....
Use only distilled water.
Forget any
antifreeze
Use Prestone water pump lubricant/rust inhibitor when system is empty then ad distilled water, that's it.
Don't use Water Wetter, it is nothing more than a soap like substance that has been known to cause head gasket failure.
This is not only my opinion but the advice of my engine builder that has over 30 years experience.