When water enters a drain pipe, it needs to go somewhere. The flow gate attaches to either 3” or 4” hub sewer and drain fittings, and pops up when the pressure of the flowing water hits it, allowing the water to discharge. Once the water stops flowing, the flow gate closes again blocking anything from falling in. Just press the flow gate into the pipe, and forget worrying about finding debris, rodents, or anything else you don’t want in your pipes. Fade resistant, available in green.