Subdural posed a question on The Wall at HeatingHelp.com in the Strictly Steam section, where some of the sharpest knives in the drawer post every day. The question was about a drop-header, and if you don’t know what that is, I’ll do my best to help you understand.

Back in the day, the steam boilers were much larger than they are now. They had very wide sections so the steam could rise up through the water without causing a lot of turbulence on the surface. They also had much larger steam-disengaging spaces so the steam could leave the liquid water behind as it headed for the radiators. And those wide boiler sections were able to accommodate bigger pipes that rose to the horizontal steam header. That was important because the wider pipes kept the steam’s velocity low as it left the boiler. The faster steam goes, the more likely it is to lift the liquid water with it, and once that water gets into the pipes, it causes the steam to condense. That means you get less steam reaching the radiators, which leads to higher fuel bills, and more liquid water in the mains, which leads to water hammer.