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DWV for near boiler piping

mjstraw Member Posts: 30
edited October 13 in THE MAIN WALL
Mid-70's(?) Burnham Holiday boiler feeding gravity conversion system with 2.5in mains. While draining my compression tank the other day, I got studying the near-boiler piping with an eye towards redoing some things (pumping away, adding a zone).

Even though the boiler tappings are 1.25in, they used 1.5in to tie it into the mains.  I was surprised to discover a faint "DWV" printed on yellow on one piece.

My guess is it was cheaper than 1.25 L or M, or they couldn't get 1.25in, or the DWV is what they had in the truck.  The fittings look like brass DWV fittings, too.

No problems, just curious.

Indiana PA


  • Jamie Hall
    Jamie Hall Member Posts: 16,514
    Well, they probably shouldn't have, but for a heating system it's probably fine.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 8,646
    They may have had overstock of copper DWV piping, it may have been going out of fashion as PVC came in or it was cheaper than type M at that time.

    As Jamie said probably not not to worry about not running very little pressure.
    You might notice that the bury of the copper into DWV fittings is only about 1/2 of regular fittings. Not to worry about that either as I have seen some DWV fittings on water supply at 40 PSI with 50/50 solder (not that strong)....still holding after 50 years.
    EBEBRATT-Ed Member Posts: 9,616
    What @Jamie Hall said

    I have seen this done many times without issue.

    It proves it was installed by a plumber

    I don't know the difference between DWV and "M" tubing (as far as wall thickness goes) which is commonly used in heating systems except the DWV fittings have less socket depth. I am sure it will hold 30psi
  • mattmia2
    mattmia2 Member Posts: 3,588
    I suspect the sweep of the bends is longer on the DWV fittings.
  • mjstraw
    mjstraw Member Posts: 30
    Looks like shallow socket but not long sweep.

    Indiana PA

  • mattmia2
    mattmia2 Member Posts: 3,588
    edited 8:08PM
    I think the sweep is a little bit longer than a pressure fitting but not much. The hub is usually almost touching on a pressure fitting. There is a long sweep 90 that is much longer.