I agree with George. The ballast will only "leak" up to the waterline level inside the ballast tank. If you have your ballast vent plug securely inserted, the ballast will only leak out of the bottom drain, and then, only when you heel. It will then slowly refill when you level out. Before you change your gasket and if you are still out of the water, give the gasket a quick inspection. Look to see of the gasket surface is clean and flat. Wipe it off with a clean wet cloth. Also wipe down the opposing hull surface. Then, line up the "indexing" pin and tighten the ballast valve really tight. Finally, fill the ballast up with fresh water with a garden hose. Check for leaks. It's a good chance you fixed your problem with the above actions. If it still leaks, but fairly slowly, plan a gasket replacement for a time that is convenient for you. Measure the gasket so you can find some red gasket material locally and cut it on you own schedule for later replacement. In the meantime, enjoy sailing! It's not going to hurt anything. BrianW