Abstract: An improved gate valve is described. The valve utilizes a flat gate having a beveled edge which slices across a central passage in the valve housing when the valve closes. A manifold is disposed in the passage to direct a purge stream of fluid across the beveled edge as the gate closes. The valve housing consists of upstream and downstream housings which are intended to be bolted together. The adjacent portions of the housings form a first slot in which the gate is slidably received and a second slot downstream of the second slot is formed in the downstream housing. In one embodiment a seat is slidably disposed in the slot which extends laterally across the passage parallel to the gate. In another embodiment the slot extends axially along the passage and the seat is cylindrical slidably retained therein. In the cylindrical seat embodiment the seat is reversible.