Control Valve in Gas Forges Posted June 6, 2019 Simplest is to just cut a slot in your pipe (I am using PVC from blower to gas inlet) and drop in a piece of sheet metal. basically a simple gate valve. You can also try a motor controller. If it is a basic brushed AC motor, should be able to try that. Harbor freight has a cheap one sold as a Router motor speed control. I have a leaf blower I'm trying to use but even with the 2" pipe blocked down around 90% it was still too much air for my burner. Could not get the forge lit and that was on lowest setting.