Flush Pro Valve - 1". Finally! Freshwater flushing of your inboard is as simple as connecting a garden hose.. Features:. Polymer. Stainless Steel Spring. Flush your boat engine safely and easily. Transparent body allows for visual inspection of water flow. Durable check valve system activated by water pressure from a garden hose. Check valve automatically shuts off hull intake when water pressure is applied. Adapter supplied with Flush Pro make winterizing your boat easy. Can be used with on board generators. Available for Standard 1" Hose Sizes