Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Hoffman No. 9 Drip Trap

The blueprints (ca. 1933) for our 2-pipe steam system show a Hoffman No. 9 Drip Trap at the end of each steam main (main splits into two that go down each side of the house). These are long gone, replaced with Hoffman F&T's. I'm looking for some more info on the No. 9's - pounds condensate/hour, principle of operation, etc. I'm getting water hammer at some risers near the end of both mains, using the example in LOSH, they *appear* to be sized OK.

THANKS everyone,



  • Christian Egli
    Christian Egli Member Posts: 277
    No 9, don't know


    I can't see why the current Hoffmans would not be good enough. Do they still work properly? Maybe some gunk is clogging them and making them sluggish. They are easy to open up, clean up, and fix up.

    Is there the right pitch on your mains? No sagging? Has insulation been removed which would cause excess condensation? When does the water hammer occur?

    There where Hoffman 590 series.
  • John G_2
    John G_2 Member Posts: 3

    My 1923 Hoffman Data Book says the No 9 "Return Line Valve" was "suitable for 600 sq. ft. of cast iron radiation."
This discussion has been closed.