When sweating copper, should I use propane gas in the blue cylinder or and propylene gas in the yellow cylinder?
Either one will work. The difference is that propylene in the yellow cylinder burns hotter. It has a flame temperature of 3,600 degrees F opposed to 3,450 degrees F for propane. A hotter flame means it can heat the pipe faster so it is ready to solder sooner. The higher temperature can also overcome the effects of a small amount of water left in the line, which is common in plumbing retrofits. The negative of propylene is the cost: about three times that of propane.
