An adsorption gas dryer has a first drying tower and a second drying tower each having a first port and a second port through which gas can pass into or out of the tower, a first manifold and a second manifold connected respectively to the first and the second ports of both towers, the manifolds each including integral gas passages, each port of the towers being in communication with a gas passage, and the manifolds each including at least one integral valve seat upon which a valve actuator is mounted to constitute a valve for controlling flow of gas through the gas passages, wherein the second manifold has two exhaust valves for controlling purge gas.
