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.

Another antique plumbing question(fine thread brass)

Vitaliy2 Member Posts: 4
Good afternoon everyone!
I'm a caretaker of a 19th century victorian mansion in New England. There's quite a bit of threaded brass pipe still in service(essentially all hot water lines and some cold water as well).

Recently, I needed to replace a failed CI drain line to a utility sink in the basement laundry room. After repairing the floor slab, the sink now sits about an inch higher than before(the floor is concrete, with a layer of asphalt on top and the sink legs were embedded in that asphalt)

Long story short, I need to shorten two brass nipples that lead to the unions that connect to the sink(of course I can just redo all of it in copper, but as an engineer, its more important for me to preserve mechanicals than even interior finishes in this house)

However, I quickly realized that both the nipples and the fittings(valves and unions) are not NPT. Here it is compared to the regular NPT brass nipple:

After some research, I found a mention of 'fine thread brass'(https://www.plbg.com/forum/read.php?1,456635) that was common here in Boston area. That does seem to fit the bill.

Does anyone have any experience with it? Is it possible to get dies for this type of thread? Or maybe there's an official name for it, so I can determine what the pitch and so on is and then maybe cut it on a CNC lathe or something.

Thank you very much!


  • mattmia2
    mattmia2 Member Posts: 5,997
    I'd just shorten the copper be low it, looks like you have plenty of room for that.

    You could always cut the threads on a lathe.
  • neilc
    neilc Member Posts: 1,818
    I get the "love of the old building" thing,
    but, aren't you feeding a new stainless basin, with no historical value?
    known to beat dead horses
  • mattmia2
    mattmia2 Member Posts: 5,997
    Unless they want to replace all of it, they will need to transition to it eventually. I suppose you could thread one end of an old piece npt then use modern fittings from there. heat it with a torch to anneal it first.

    Might want to look in to why on this old house in like 1982 they said you were really lucky that fine thread brass didn't crack.
  • Vitaliy2
    Vitaliy2 Member Posts: 4
    edited April 2021
    I believe the stainless steel sink is fairly old too. This house was a doctors residence for much of the 20th century and the carriage house was the clinic. The room in the picture was the main laundry for the whole operation. They pretty much stopped by 1960s so the sink must be from that time
  • Vitaliy2
    Vitaliy2 Member Posts: 4
    The brass is in a decent shape. Didnt have much issue disassembling everything
  • Jamie Hall
    Jamie Hall Member Posts: 19,423
    I've seen that fine thread before... in fact, I have some. But I was fortunate in not having to try to fit it to a modern fitting. I've looked all over, and I'm sorry but I can't find the exact spec. on it. If you can determine the thread profile -- it may be a V rather than the modern NPT rounded profile -- a clever chap with a machinist's lathe could duplicate it. If you have a really first class railroad model hobby shop around, you could ask if they know of someone with a Unimat...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Pumpguy
    Pumpguy Member Posts: 551
    edited April 2021
    As @Jamie suggested, anyone with a screw cutting metal lathe would be able to cut those threads for you.

    Aside from professional machine shops, you might check into the home shop machinist and model engineering fraternities. There are several forums found online.

    If you still need help, contact me via PM or phone at number below. I should be able to do it for you.
    Dennis Pataki. Former Service Manager and Heating Pump Product Manager for Nash Engineering Company. Phone: 1-888 853 9963
    Website: www.nashjenningspumps.com

    The first step in solving any problem is TO IDENTIFY THE PROBLEM.
  • mattmia2
    mattmia2 Member Posts: 5,997
    You could also figure out what copper tube or fitting size will slip over the outside of the brass and sweat it to the copper then adapt from there.
  • ChrisJ
    ChrisJ Member Posts: 13,258
    If it was mine I'd either be modifying the sink, or those copper lines.
    I'd probably already have two couplers on the copper lines, to be honest.............

    I really do not think you want to go the machine shop route.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    JUGHNE Member Posts: 9,908
    IIWM, I would cut about an inch (as needed) out of the copper tubes that comes out of the top of the sink, solder in a coupling for each and there you are.

    IMO, you are over thinking this.

    The copper and sink are not original to the house anyway.
    The sink is old, probably from the 60's as you guess.
  • Vitaliy2
    Vitaliy2 Member Posts: 4
    Thanks for great thoughts and ideas everyone! Yeah, cutting and resoldering copper was my original plan, and I will probably end up doing that. But fine thread brass got me excited since I haven’t dealt with that before and thats exactly the kind of craziness I like to do(along with pouring cast iron lead joints just for fun)

    Its unfortunate that theres so little info about it. I also wonder if some antique threaders/chasers I see at flea markets and such are for this type of thread.
  • neilc
    neilc Member Posts: 1,818
    Vitaliy2 said:

    along with pouring cast iron lead joints just for fun

    ah, pouring and huffing lead are ya?
    starts to explain your fine tread brass desires,

    known to beat dead horses