Abstract: An apparatus for conveying a process gas stream from an upstream source to a downstream treatment unit, including a manifold receiving gas from the upstream source, including first and second valved inlet lines which are alternatingly employed to flow gas to a downstream process. The manifold is arranged so that one of such lines is actively flowing gas from the upstream source to the downstream process, while the other is blocked by closure of the valve therein and is undergoing regeneration. A pressurized water source is coupled with the manifold, by valved water flow lines to each of the first and second inlet lines, with the water flow line valves being selectively openable or closeable to establish or discontinue flow of pressurized water therethrough, respectively. Cycle timer control means are employed to control the operation of the manifold and valves, for water cleaning of the off-stream inlet line.