There are typically three electric ball valves; ½ inch, ¾ inch,1 inch, and11/4, 1½ inches. The size you need will depend on the project you are working on. For instance, if you're installing an outdoor faucet with a hose bib, then the size will most likely be around ½-inch or ¾-inch. If your project involves plumbing for a bathroom sink that has two sinks, then it's more than likely that you'll require a 1-inch valve because there's always water running in both pipes at any given time... Electric valves are a vital part of any electrical system. They control the current flow, allowing it to be turned off or on at will. However, not all ball valves are created equal. So it is important to know what you need before making a purchase decision.