An in-line parts washing system comprising concatenated modules of two discrete lengths where certain of the modules have a self-contained tank of parts cleaning chemical along with a motor-driven pump for forcing the cleaning chemical through spray heads enclosed in a shroud through which the parts to be cleaned are transported via a conveyor. Other modules disposed in-line with the wash modules provide zones where the cleaning chemical dripping from the parts is collected and redirected back into the tanks from which it originated. The ability to swap modules of differing length allows a user to easily alter the cleaning process.