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.

Flange gasket material?

bnlacava Member Posts: 2
Hi everyone. I have a flange connection between two pipes on a single-pipe residential steam system that has rusted out a bit and leaks, so I want to break it open and replace the gasket but I can't find much info on Google about it. All my searches just come up with stuff for industrial steam systems. My "We Got Steam Heat" book isn't much help either. Here's a picture of the flange:


Any recommendations on a material or supplier for this?

Perhaps I should also ask if replacing the gasket will even help to begin with, or if I'm barking up the wrong tree?

Thanks in advance for any info.


    EBEBRATT-Ed Member Posts: 15,539

    That is not a flange, it's a flange union. They are sold as a set and are assembled with two flanges, bolts and a gasket all sold as one assembled part.

    As far as I know the gasket is not sold separately. The old gasket likely contains asbestos. If the flange has been leaking the face is likely rusted and pitted and won't seal.

    My advise would be tie the pipes off with a rope and use a come-a-long to gently spread the pipes apart you only need an inch or so. Cut the old flanges off with a grinder and a cutting disk and replace the flanges.

    The average supply house may not know what a flange union is but you can order them if not in stock
    HVACNUT Member Posts: 5,841
    I've never had the need to attempt that but I assume you'd have to be very careful not to cut into the threads. I'm just asking, but if he supported the piping like you said, would it be better to start the cut(s) before the dismantle, then separate and continue?
    JUGHNE Member Posts: 11,062
    I had a 4" flange dripping......but after dropping the steam pressure down from 5 to 2 PSI, the leak stopped.....lucky.

    I did find gaskets for others though.
    The real challenge is getting the flanges far apart enough to clean the surfaces.
  • SlamDunk
    SlamDunk Member Posts: 1,581
    If mcmaster-Carr doesnt have what youre looking for, it may not exist.
  • bnlacava
    bnlacava Member Posts: 2
    Ok thanks for the info!
    EBEBRATT-Ed Member Posts: 15,539
    @HVACNUT , I have good luck with a grinder with a cutting disc. Those flanges are cast iron and cut like butter. Cut most of it to take the strength out of it then break it like any cast fitting with two hammers. I would separate first


    You can tell a "flanged union" because they use square head bolts. Also the tel tale is the bolt heads recessed in the flange. Also the flange diameter is different from the regular "companion Flanges"that bolt up to valves and flanged strainers and pumps etc.

    I have never seen the gaskets sold separately but they might be. I have only seen them sold as a unit. Two flange halfs with bolts and gaskets
  • Fred
    Fred Member Posts: 8,542
    edited June 2019
    I've had to replace the flange union gasket before. They are available at most plumbing supply's, at least here locally. If the flange halves are not pitted, you can just replace the gasket but you should also buy new flange bolts also, at the supply house. Buy the same size bolts as are there now. If the flange halves are pitted, replace the whole thing.
  • nibs
    nibs Member Posts: 511
    If you need to make a new gasket, I have some fairly thick epdm material, either 40 or 80 mil if I recall. If you need some let me know what size & I will mail you a piece. I can let you know how thick if interested.
  • Harry_6
    Harry_6 Member Posts: 141
    Strictly speaking, they are "companion" flanges. You can buy them individually, but in your case you need a pair. You can get them with or without appropriate bolts and gasket, although there are many thicknesses and types of gasket material available in sheet form that would work perfectly well. In that case you'd have to cut the gasket yourself. You can either get a circular gasket that fits inside the bolt circle, or a "full face" gasket that is the O.D. of the flange and has holes pre-punched for the bolts. Whether purchased or cut, I prefer the one that fits inside the bolt circle, as its smaller area equates to more compression per square inch.

    As was said earlier, you might be able to pull it apart with a come- along, but it's impossible to tell from the photo. Regardless, I'd cut mostly through the cast iron flange(s) with a grinder cutoff wheel then whack it with a sledge, and those puppies'll split right in half. The problem lies in screwing the second one on, since that's where you have to pull the pipes apart to get clearance to start it on the thread. The rest is cake.

    An alternative is to just get it apart enough to clean up the faces (still no small trick) with chisel and file, and then just replace the gasket. The best option there is to get a graphite gasket, which will conform very well to slightly damaged faces and never stick in place. Ever.

    But I'd probably replace the whole thing.
  • Pumpguy
    Pumpguy Member Posts: 659
    +1 on EPDM gasket material. It's good for 300* F. and resistant to Amine based water treatment chemicals. I've found it seals better on pitted cast iron surfaces than common non-asbestos composition gasket material. EPDM gasket material is a much better choice than red rubber where high temperatures are found.

    Apply to clean dry surfaces. Don't use any sealers like silicone or Permatex. These sealers cause rubber type gaskets to squish out from between the joint faces.
    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.
    EBEBRATT-Ed Member Posts: 15,539
    This is an old post. And they are not companion flanges