A gas delivery system includes a 2-port valve including a first valve located between a first port and a second port. A 4-port valve includes a first node connected to a first port and a second port. A bypass path is located between the third port and the fourth port. A second node is located along the bypass path. A second valve is located between the first node and the second node. A manifold block defines gas flow channels configured to connect the first port of the 4-port valve to a first inlet, configured to connect the second port of the 4-port valve to the first port of the 2-port valve, the third port of the 4-port valve to a second inlet, the second port of the 2-port valve to a first outlet, and the fourth port of the 4-port valve to a second outlet.