Plumbing for potable and raw water systems on cruising boats are separate and distinct systems. Potable water is brought aboard through watertight deck fills and held in metal or plastic tanks. It is delivered to faucets on deck, in head compartments or the galley by water pumps. Sometimes it is run through a filter before reaching faucets. Potable water may also be made aboard, using a reverse osmosis watermaker. Raw water systems use the water in which the cruising boat is floating, either to cool equipment like engines, generators, and air conditioning compressors, or to wash down exterior decks. Hoses for potable and raw water applications differ, and should be specific to the intended use.