A de-header valve can include a flushing system for flushing undesirable material from the upper and lower bonnets while the de-header valve is opened. The flushing system can include three valves. A first valve controls the flow of steam to the de-header valve. A second valve controls the flow of water for flushing the bonnets. A third valve controls how the bonnets are drained. The third valve can be a three way valve that allows the bonnets to be drained to a pit during flushing, and also allows steam condensate to drain into a steam trap.