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New radiator Union slightly shorter

physwm2501 Member Posts: 4
edited October 2018 in Radiant Heating
I recently had to remove 3 of my radiators to have the flooring company add carpet and vinyl flooring.

When I reinstalled them I replaced 3 of the valves since the old ones no longer operated

On first fill 2 of the old unions had a slow leak and one of the new valves had a leak at the spud.

For the sound leave I removed applied an reaplied and extra wrap of tape and turned another half turn farther.

For the 2 leaking unions I replaced with new ones but they are about an 1/8in shorter then the originals and won't line up. Upon shopping at 3 different supply stores I can't find one with a longer spud. What's the best way to address the issue?

Can I remove the spuds and use pipe gope instead and try not putting the spuds as far in? In both situations I have no more play in the pipes.


  • physwm2501
    physwm2501 Member Posts: 4
    I was able to get the living room radiator hooked up with a slightly different brand union and spent about an hour increasing the hole size through the floor to give me a tad bit more play. In the end I could start the threads by hand on both sides and only needed a little torque to move the pipes in.

    Trouble now is the spud is leaking on the elbow side where it wasn't the day before, I had reinstalled it to try and get more length. I'm going to remove the spud and instead of just applying thread tape will add some pipe dope on top as well. I'm confident another 1/4 to 1/2 turn will seal it up as it was dripping about a drop every other minute.

    I put the old union back on the bedroom radiator and still had issues with leaks even after smearing some pipe dope on the union. This morning I removed it and applied a bead of of rtv silicon ultra gold and reconnected the union. Going to let that cure for 12 hours and then tighten another 1/4 turn. I hate to use a sealer on the union as the rest of my unions are sealing fine but unless there is another option I'd have to repipe the return.

  • rwilson2526
    rwilson2526 Member Posts: 16
    At least on the ones with the Horizontal valve it looks like copper pipe in and out? You could cut small section out of the return line, move the radiator to the left and sweat in a coupling maybe.Or lengthen the supply pipe with a coupling as well I would guess?
  • physwm2501
    physwm2501 Member Posts: 4
    That is what I'll have to do if the rtv doesn't do the trick on the leak and I need a new union. I can take a picture but the supply and return is still steel. There is a tee that branches off to this radiator and the other side of the tee is copper to the upstairs as that was added in the 70-80's.

    The other 2 branches of the tee are still steel.

  • Tinman
    Tinman Member Posts: 2,808
    Increase the size of a floor opening just a little bit and use escutcheons.
    Steve Minnich
  • rwilson2526
    rwilson2526 Member Posts: 16
    Ah... didn't realize there was a tee back there. Not as easy as I made it sound. I had a similar problem when I did my floors except my new valves were too low.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    edited October 2018
    That’s why we advise everyone to repair rather than replace valves.—NBC
  • physwm2501
    physwm2501 Member Posts: 4
    Well heat is back up, just in time for these 30° lows the next few days. The rtv did the trick on the bedroom unit and giving that spud another half turn sealed up the other leak.

    My third unit I'm noticing a small leak now on the union elbow. Probably about a drip per hour but I need heat for my tenants so have a cup under the union for now. Gave the nut another quarter turn and have either slowed it down or sealed it.