............Not sure about using RMI-25 with just water. According to their web site is restores the buffers and such in the anti-freeze. Redline WaterWwetter may be a better choice......................RemoveBeforeFlight
I may not know about a lots of other stuff, but I do know a LOT about cooling systems and RMI-25 after working on vehicles for 40 years in the desert, and RMI-25 is the best radiator additive on the market you can find.
We have local GN radiators over 20 years old that act and look like new, including my 9000 mile T-type. It is the only additive that will properly protect the radiator and cooling system while cleaning at the same time, and it is NOT caustic.
Before I found RMI-25 in the 90's, I was using WaterWetter and found it did not contain enough additives to prevent corrosion in the radiator as it actually removed solder from the joints over a period of time, especially in a low-use car.
When used properly and consistently, you will have excellent service from the cooling system as we almost never replace a water pump, heater valve or other items in vehicles with a steady diet of RMI-25.
Since it contains a surficant which allows better heat transfer, your vehicle will run cooler, and I have had reports of up to 25 degrees improvement after a flush or 2 with RMI.
In my new vehicles, I always add an 8oz bottle every year, and the coolant looks like new at trade-in time, and they run cooler too!