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Leaky overtightened union

joe_94 Member Posts: 39
In replacing a hot water radiator which has one half inch piping,  I greased the union's collar's threads. It tightened so smoothly I overdid it. It is fully tight. But, It drips a little bit.

 It is [or was] a nice looking 70 year old ground union with a brass insert seat.

Q: Can I re-open it and put hi-temp silicon on the faces?  Or is it time to buy new?

 [ which I hate to do as it may throw this tallish, narrow rad visibly out of plumb. The risers come vertically into the space. These are straight unions, not els.New unions look shorter.]

Home repair gives me useful humility



  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    Trouble with the union

    Try greasing the faces of the union this time, and as you tighten the collar, rock the radiator gently to allow the faces to align them selves, and you should be ok. Ouse dish washing liquid, instead of grease.--nbc
  • icesailor
    icesailor Member Posts: 7,265
    edited May 2012

    The "Insert" you mention is probably an Orifice to slow down the water. You need to remove it and very thoroughly clean it, and the faces of the union. That means cleaning by whatever means required, to clean all the crud off the face of the union. Then, use a clean can of pipe thread lubricant like Rectorseal #5 on ALL surfaces. Don't bother with the union threads. You already have enough crud on it.

    Do NOT try to prove to yourself that you have the strength of the old dead guys and tighten the union with a 2' pipe wrench. You have already stretched it. It's not brute force, it finesse.

    "Grease" doesn't cut it  and never has for me.
  • Paul48
    Paul48 Member Posts: 4,469

    opted to replace in a similar situation.I had to crack the unions so I could tip the radiator forward to free a cat that was stuck upside-down between it and the wall.Nothing would make it stop dripping, and it's an old converted gravity system with a huge volume of water.Since I had to drain the system, I figured get it done in one shot.The house is 90 years old,on a rubble-stone and brick foundation in a sandy soil. Just getting the new union reasonably aligned before tightening took 2 men, a mule and a lot of swearing, because the house had settled so much.Good Luck....Ain't Homeownership Fun!
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