Since the purpose of an engine cooling system is to keep engine parts and working fluids at safe operating temperatures, you must take preventive actions to keep corrosion and scale formation to a minimum. To help prevent undesirable operating conditions in an engine, you must meet two basic requirements. First, you must use an acceptable type of water for the cooling system. Second, you must chemically treat the water with the proper corrosion inhibitor.

WATER

When you fill the freshwater cooling system of an engine, you must use an acceptable type of water. An important part of a coolant treatment program for any engine is the use of water that contains minimum amounts of hardness, chloride, and sulfate. The water you must use for filling or topping off cooling systems or for mixing treat-ment chemicals is indicated by the following categories:

1. Shore source water that meets the require-ments of Naval Ships Technical Manual, chapter 220, volume 2, for shore-source feedwater.

2. Shipboard boiler feedwater or condensate that meets the requirements of Naval Ships Technical Manual, chapter 220, volume 2.

3. Water produced by shipboard distilling plants, demineralizers, or reverse osmosis units.

4. Water produced by shore-based distilling plants, demineralizers, or reverse osmosis units.

If water indicated by these categories is not available, use clean, fresh water. Clean, fresh water includes shipboard potable water or city water.