Steam, one pipe radiator leaks at connections

Penny

We had an old radiator moved as part of a small addition to our kitchen.  New steam (one pipe system) piping was brought to the radiator and connected.  The radiator functioned fine last spring after the install as well as this fall.  It recently started to leak at the valve joint (?).  My husband disconnected the radiator, applied pipe dope and reinstalled and tightened.  The leak was gone for a day, but then back again in the same spot and now too at the nut below the control.  Any suggestions on how to properly fix the problem?  I'd prefer not call the plumber back out so long after install for such a (seemingly) small problem.  Should my husband disassemble and clean (how to do properly?) the threading, etc...before attempting to fix again?  Use of pipe dope correct?  I've attached a photo (not the radiator in question, but just as a diagram to point out where the leaks are-they are masked in yellow).  Any help would be great!

Thanks!

Big-Al_2

RTV

I have run into this too. The important thing to remember here is that the seal in a union is made by the mating faces, not the threaded part of the connection, so putting pipe dope on the threads doesn't help.



Here's what to do:  Loosen the union nut all the way and move the radiator away from the valve a little.  Move the nut out of the way and clean up the faces of both parts using steel wool, Scotch Brite, or very fine sandpaper. Before reassembly you can put a little pipe dope on the faces . . . or better yet, use a little RTV silicone gasket sealer available in the automotive section of most any hardware store or auto supply.  The RTV will hold up to 600 degrees and peels right off again if you ever need to take things apart, and there's no risk of any oil from pipe dope contaminating the system.

Chris M_2

Seems Hubby Did Everything Right

I'd disconnect the radiator from the valve again, re-dope it with teflon tape-dope, and tighten it all up again.  For the valve handle, try tightening the stem nut down a little more.. a little bit at a time (1/8th turn), and see if that helps out.  If not, I'd replace the valve altogether.  They're cheap enough. 

BobC

Bonnet nut leaking

Al's fix for the union leak sounds good to me. Just make sure the valve and the radiator line up squarely before putting it together.



The other leak is where the stem goes into the bonnet nut. Tightening that nut might work but the packing under the bonnet nut might have to be replaced. You can buy valve packing at a hardware store, it's a graphite coated string that you wind around the valve stem before tightening the bonnet nut.



Bob

Big-Al_2

Teflon Tape

In a pinch, when I couldn't find my little spool of packing string, twisted up teflon tape seems to work OK.  I've just removed the packing nut and slid it up toward the handle, twisted up a foot or so of teflon tape to look like a string, and wrapped it around valve stem.  When the packing nut is re-tightened, it compresses the new teflon into the existing packing and the whole works seals off the stem.  Yes, it's kind of hack, but since these radiator valves are left wide open all the time anyway it's not going to wear out in my lifetime.

Bill_110

video on rad valve hookup

You might want to view the following video to get a visualization of what Big Al and the others are suggesting. I had to take off a tailpiece and a valve off a nipple on a probably 80 or so year old installation and without the advice and encouragement that were given to others on this subfect here on heating help I never would have managed it. I found the Old House video link to be very helpful to. Even though the part about getting off the spud (on an old installation anyway) is pretty unrealistic, by following the other instructions I was able to get the thing working without a drip the first time. It seems to be holding up after several months of use.





p://www.thisoldhouse.com/toh/video/0,,20258687,00.htm