Strainers are used to filter out the unnecessary within a plumbing system. Y strainers are pipe fittings that are used for many applications ranging from cosmetics, to food preparation, diesel engines, and the petroleum industry. They have a filter inside that traps elements within the plumbing system. A foot valve is a type of check valve, which means it flows in one direction, which is coupled with a strainer. They are usually used for plumbing systems where liquid needs to be pumped from a lower level holding area, such as a water well.