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Old hot water radiator (butterfly) valve leaking?

Ocelaris Member Posts: 26
edited June 2020 in THE MAIN WALL
I have an old radiator valve on our hot water system from the 1950s and can't for the life of me find a replacement (or what it's called). It's 1/2" mpt x 1/2" sweat (or 3/4" for larger radiators) (Pictures attached) and is inline. It was an old Monoflow system that I converted to last/first loop zones and it has been working great as I divided up the house, added a few more zones and radiators in the basement. BUT... as I try to make my kid's rooms warmer I played with these what I assume to be butterfly valves, and they started leaking. Can anyone point me in the direction of a replacement? I know I can do thermostatic radiator valves, as I put those in on every radiator in the basement, but was hoping it was as simple as packing grease or something. As you can see, I don't have a lot of room to work with. The depth of the radiator is all I have to use unless I start hacking away at the grill which normally covers it; so I was hoping to find a similar small form factor valve to replace it.

Thank you!


  • Jamie Hall
    Jamie Hall Member Posts: 23,272
    More likely a ball valve. In any case, you can almost certainly substitute one, though you may have to provide your own sweat to thread coupling. See what you can find here: https://www.supplyhouse.com/Ball-Valves-5000
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 22,105
    A six point socket may be able to remove the packing nut and replace the o ring. Some older valves had graphite string packing. System would need to be drained down first

    Worse case you replace but with that union end it may be a major repair
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Ocelaris
    Ocelaris Member Posts: 26
    Thanks, I only have about 5" to work with, so I'll look at the ball valves, but first I want to take them out and try re-packing them. It definitely looks like it's leaking out the threads, but I don't have much to lose at this point.

    I've wanted to replace these valves for a long time, but sweating under the radiators isn't something I'd pick up without reason. With more than a dozen radiators, leaving a sleeping beast lie has been the best choice up until this point. But I think it's time for me to sweat some pipe if the repacking doesn't work.

    I wasn't going to confess, but what got me into this mess is watching Bob's video on cleaning the Caleffi 537 backflow preventer... long story, but the house's high pressure and irrigation valves were irritating it and I took it apart; tested it and some how the pressure went up to about 50 psi before I noticed ... they leaked a little before if I tweaked them, but never more than a thimble full. I have a taco 4-way mixing valve, and I suspect when I was test running the system with that valve fully closed the pressure built up (expansion tank on the wrong side of the mixing valve) and the packing just got bypassed.

    I was thinking of the caleffi radiator valves (I love Caleffi!), but the control valve is so huge, I'd never be able to fit one under there properly without hacking away the grill... I'd love to have one in my daughter's room, but I'll have to see if the wife approves.

    Thank you!

  • mattmia2
    mattmia2 Member Posts: 9,622
    You could orient a new valve with the stem down or up if you don't have enough clearance to the front. You can almost certainly repack it if you use a good 6 point socket to take the packing nut out. Even a lot of modern ball valves use a teflon packing washer under a packing nut at the stem.
  • Alan Welch
    Alan Welch Member Posts: 267
    Before you tear it all apart, try tightening it, you might get it to stop.
  • Ocelaris
    Ocelaris Member Posts: 26
    Thanks, I will take it apart next week when it's a bit warmer here, still getting down into the 50s at night. I hate sweating 60 year old corroded copper in a tight place, but that might be in order if I can't figure the packing out.

    The taco 4 way mixing valve was seized, took a pair of lineman's pliers to it and gave it to the few turns and good as new. Although that worries me that at 5 years old I'm seeing some seizing. But the wife says we're not getting a modcon anytime soon, so it'll have to hold up! Thanks!
    JUGHNE Member Posts: 11,058
    I have dealt with valves like this, they are from 1961.
    If you loosen the nut with that 6 point socket and then rotate the stem around several times while it is dripping then tighten it up with the socket when it is open it may stop dripping.
  • Big Ed_4
    Big Ed_4 Member Posts: 2,780
    If you need to repack , remove the nut and wind teflon tape tape around the valve stem a few times and use the packing nut to push it in . Not too much ,you need the nut to catch treads and don't over tighten the nut . You do not want to split the housing . You can always add more ...

    Normally you never need to touch them becuase they are terrible for regulation and only shut off one end . They are more on or off . The easiest way to adjust output on a convector ,is to adjust the convection . Covering the top of the rack of fins with aluminum foil , or if your lucky enough to have the upper dampers . I seen very few over the years that were installed .. Maybe they were not offered on some brands . The units with key way in the top center of the cover used ball chain to raise or lower the damper .. I thought they must have be a pain to install for the lack of finding them....
    I have enough experience to know , that I dont know it all
  • Ocelaris
    Ocelaris Member Posts: 26
    edited July 2020
    Just wanted to share that the graphite packing string worked great. I'm still not sure what's inside the valve, but it was clear water was getting out next to the screw adjustment. I had to drain the system to replace an emergency pressure valve anyways, so I packed all the valves on the zones that we would adjust. It was a 16 and 18mm socket that did the trick on 1/2 and 3/4" valves. Strange that my dad's old imperial fractional sockets didn't fit! Thanks again!