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.

Threaded flanges leaking

Big Will
Big Will Member Posts: 396
We have a job with flanges around the pumps. All the pump flanges and butterfly valves are sealing just fine. The only flanges we cant get to seal are The black iron flanges with nipples in them. two of these mate too a globe check valve and two mate to a Y strainer. We have re set them twice now. We replaced the paper gaskets with neoprene but that did not help. the next thing is to double up the gaskets. I have never had this much trouble with a flange before. The funny thing is the leaks have been out of the bolt holes not the flange face. Any insight would be help full

PS we are using full face gaskets.


  • Charlie from wmass
    Charlie from wmass Member Posts: 4,322
    try not using full face gaskets.

    the extra leverage you get having the bolts outside of the gasket may help draw them shut. Have you checked for cracks or sand holes ( if they are cast iron)in the flanges? How square are they to start with?
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • David Sutton_6
    David Sutton_6 Member Posts: 1,079

    Are all your bolts even? the slightest list in the flange, one bolt alot tighter than the other may cause leaking,
  • Wayne Heid
    Wayne Heid Member Posts: 49
    Nipple depth

    Any chance the nipples extended beyond the flange face when tightening and are preventing you from fully making up the flanges?
  • hot_rod
    hot_rod Member Posts: 22,143

    they need to be square to one another the gasket will not make up for crooked alignment.

    What about expansion and contraction movement? excessive pressure, maybe not enough expansion tank capacity?

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Big Will
    Big Will Member Posts: 396
    edited August 2010
    Ye haw

    SO we went to steel ring gaskets between the Y strainer and flange easy money. However the other side of the pump is a globe style silent check valve. these have two screws in the face of the flange that hold the brass check in place. those screws line up with the flange bolt holes. It leaves about an 1/8th of an inch. between the flange bolt holes and the set screw. Could not get it to stop leaking out the bolt holes. We assembled the whole thing and blank flanged the ends. Ended up using two neoprene gaskets and getting a good seal at 125 Psi in a immersion test.  I hate having to use two gaskets it feel like defeat. However it has held for two days now. With all of the fighting with it last week I am calling it done. I will say I have never had problems like this with flanges its been very frustrating
This discussion has been closed.