A question asked on The Wall: "What's the point of building a drop header for a steam boiler, and what does it look like?"
The drop header keeps water from getting into the system, and allows for more expansion and contraction of boiler sections. This results in "dry" steam being fed to the system, which is steam at its most potent.
Wet steam does not do much except cause water hammer. The best results are accomplished by "drying" the steam at the header (by increasing the steams "travel" distance at the boiler). That's usually tough to do in a low basement, so a drop header can give you the best of both worlds.
Bob Young replies:
As Dave pointed out, extra dry steam is a key result and it makes piping a proper header a snap, especially if you are tight for head room. Once you do a drop header you will never probably ever do it otherwise.
Lyle Carter replies:
I've found that when I'm using an indirect water heater with a conventional steam header on a steam system that when the indirect calls for heat I can feel the steam heat in the mains, sometimes 10-15 feet away from the boiler, which means that we're wasting heat. When I use a drop header, the main doesn't heat at all.
Here's what it looks like: