Water lines or kitchen systems can get gravel, deposits that break free, and other stray items in the line. Due to the velocity of the water pushing them, they can severely damage or clog devices installed in the flow stream of the water line, for example p-traps or pipes. A strainer is essentially a screen installed to allow water to pass through, but not larger items. The larger items fall to the bottom or are held in a basket for later clean out. They normally have an access that allows for them to be cleaned or have the strainer plate or basket replaced.