Duplex fluid strainers, systems and methods are provided, and include a housing with a first valve chamber defining an inlet port, a first port, and a second port, and a second valve chamber defining a third port, a fourth port, and an outlet port. The first and third ports communicate with a first strainer chamber, and the second and fourth ports communicate with a second strainer. A first seal assembly includes a first disk movable within the first valve chamber into sealing engagement against either of the first port or the second port, and a second seal assembly includes a second disk movable within the second valve chamber into sealing engagement against either of the third port or the fourth port.