Pipe size

Charlie from wmass

That 2" capped pipe is most likely a drip that was ignored when the new boiler was installed. This would cause water hammer.

ChrisJ

Fred said:

All of the boiler gauges should be installed on a pigtail but it is pretty typical for most installations to have the 0 - 30PSI gauge installed directly into the boiler block. They are pretty much worthless for day to day operation anyway. For the sake of argument, many (if not most) of those gauges are suppose to have an "internal syphon" or so they say.

I think they do, and they are guaranteed to be completely plugged up within a few years.