Steam makes ironing more effective. It softens fibers so you can more easily flatten them with the hot iron plate. Without steam, ironing can take longer and sometimes doesn't do a very good job of getting out wrinkles or ironing in creases. This is a particular concern for people working with clothing or other fabric on a professional level.
To use a gravity-feed steam iron, hang the water tank 2 to 3 feet above the iron. Connect the tank's tubing to the iron per the manufacturer's directions. Fill the tank with distilled or tap water then add a demineralizer. While you're ironing, whenever you need steam, press the steam switch. Gravity pulls water from the tank through the tube and into the hot iron, which produces a jet of steam.
The tank on a gravity-feed steam iron generally holds a gallon of water, which provides a much larger supply than the reservoir on a regular steam iron. The high volume of steam can save you a significant amount of time if you're doing a lot of ironing. Gravity-feed steam irons are also heavier than standard steam irons, which further increases their effectiveness.
Clothing manufacturers, commercial sewing shops, dry cleaners and hotels commonly use gravity-feed steam irons if they don't have a steam boiler ironing setup. Gravity-feed steam irons cost more than regular irons and aren't very portable. If you only iron occasionally, this may not be the right iron for you. You might want a gravity-feed steam iron if you do a lot of quilting or other sewing projects that require a great deal of ironing, especially if it calls for a professional look.