Topping off your coolant with plain water kills engines!
Lee County's best price for a Flush & Fill - $79.99
A radiator Flush & Fill not only replaces your coolant with a fresh, ideal 50/50 mixture of water and antifreeze, it forces out suspended rust and built up scale - under pressure.
Different than a simple drain and fill, a Flush & Fill Flushes out , under pressure, the built up rust & hard water lime deposits (scale) on your radiator and engine block
Although we in Southwest Florida have little chance of an engine block cracking due to freezing, all engines rust without anti-freeze. The most vulnerable parts of your block are the "freeze plugs". Up north, they are designed to blow when engine coolant expands too much in a freeze.
"The problem with freeze plugs is that they are made of very thin metal, AND THEY RUST!!! From the factory they are made of galvanized steel, and if you always run a 50/50 mix of antifreeze you should never have a problem. Unfortunately many people don't do this, and the freeze plugs rust through, creating a coolant leak."
Freeze plugs, or core plugs, are first thing to rust out when the unwary fill or top off year after year with water only. At this point you can replace all your radiator hoses, etc and the water keeps mysteriously disappearing and your motor finally overheats. A Coolant Flush & Fill will stop the rust process.
At this point an expensive head gasket replacement may not do - your entire motor is rusted out from the inside, as well as a blown head gasket and warped head.
Bare Minimum: head gasket & mil the warped block - 100 times (or more) the price of a Coolant Flush & Fill!
Worst case scenario: replace the whole motor!