Steam radiator - Stripped Thread

Giants9890

Update 10/4, photos added. Some added context. A plumber previously told me he wouldn’t be able to rethread and I’ll either need to epoxy a varivalve or buy a new radiator. The new valve bought won’t fit into the whole, and the threads are gone. Not sure what to do here. 

 I’m a homeowner with very little plumbing knowledge. 

A large radiator on the third floor in my home has a stripped thread where you insert a Varivalve. My heating company told me they couldn’t tap the thread and the only good option is to use an epoxy to secure the varivalve. Does any one have any suggestions, or should I just replace the radiator? We need heat regulation as this is a bedroom and it overheats. 

dko

post photo

Waher

Post a photo. If the hole is truly stripped it may be easiest to drill and tap a slightly larger hole to accommodate a threaded brass bushing for the air vent to screw in to. There's no need to replace the radiator and using epoxy is asking to create a problem when unnecessary.

Mad Dog_2

Try screwing in a short 1/8" black nipple. That may clean it up.  If it screws all the way and and is a little wobbly but can be pulled out.  Use a lot  quick wick clockwise and lots of pipe dope. Add a 1/8" Black couple on the end.  Screw in your air vent.  Try that first.  Mad Dog 🐕 

EBEBRATT-Ed

Drill and tap it for 1/4" IPS. A decent hardware store will have the right size drill and tap. You need a 7/16 drill bit and a 1/4" pipe tap

Giants9890

Thank you everyone for the feedback. Posted photos and an update and hope to hear your thoughts. 

mattmia2

Is that a crack at the upper left? If it is cracked attempts to drill and tap larger or use a helicoil will not go well.

jesmed1

I would try what Mad Dog said before trying more extreme measures. You may be able to get it to seal by doing as he says without any further drilling or tapping.

"Quick wick" may not be readily available to you, but you can get it on Amazon:

https://www.amazon.com/Loctite-442-35082-Length-Sealing-Off-White/dp/B000ORA0MM/ref=sr_1_1?crid=2HALOURWKP1NQ&keywords=plumbing+quick+wick&qid=1696433628&sprefix=plumbing+quick+wick,aps,93&sr=8-1

And there are many types of pipe dope, but I've had good success with this:

https://www.amazon.com/Rectorseal-23631-Brush-Thread-Sealant/dp/B0002YPAFY/ref=sr_1_1_sspa?crid=1WGRNSH9WTW7A&keywords=rectorseal+t-2&qid=1696434105&sprefix=rectorseal+t-2,aps,104&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

Apply both to a 1/8" black iron nipple (with coupling for the vent) from Home Depot as Mad Dog said. You may find that's enough to seal it.

Giants9890

mattmia2 said:

Is that a crack at the upper left? If it is cracked attempts to drill and tap larger or use a helicoil will not go well.

No not a crack. Just a little rusty and old. 

ChrisJ

How far in do the vents go... meaning are they close to bottoming?

If not, then get a 1/8" NPT tap and carefully run it in, once it's started in the same threads drive it in deeper but don't go crazy. If you go too deep, then you'll bottom the connection out without making a seal. You don't want to drive the tap any further in than necessary to get good threads. Also be careful it doesn't physically hit the inside of the radiator and stop it self. You'll pull the threads out if that happens and you keep turning.

It's a tapered thread, so it's designed to wedge together.

I'd want 2 threads or so exposed when fully tight worse case. On my radiators I chased all of the threads but kept it so the vents only screw in 3 turns or so. That leaves me plenty of meat in the future to go deeper. When I got there they only went in 2 turns.

If it's stripped and too bad to clean up by going a little deeper, I'd do as others said and drill and tap for 1/4 NPT and then use a 1/4 to 1/8 bushing.

Mad Dog_2

Air vents are brass (softer) so their threads don't usually strip the cast iron female tappings.  95% of the time, my black nipple does the trick.   Mad Dog 🐕 

mattmia2

Given how thin that boss is you might be better off with a helicoil than drilling and tapping to the next size.

You could also try overthreading a nipple with a die and see if it catches something deeper.

realliveplumber

X 3 on the heli coil.

Mad Dog_2

Never used  Heli-Cat 🐈...How they work?  Mad Dog 🐕 

mattmia2

Mad Dog_2 said:

Never used  Heli-Cat 🐈...How they work?  Mad Dog 🐕 

Are you making a joke or are you really asking with a typo?

realliveplumber

Its a stainless steel insert. Resembles a wound spring. Diamond profile. Slightly oversized, and requires a special tap with a standard size drill bit. Installing a 1/8" npt heli coil will remove less material than going up to 1/4" npt.

I used a ton of them in a past life. Mostly machine threads, not many npt.

mattmia2

realliveplumber said:

Its a stainless steel insert. Resembles a wound spring. Diamond profile. Slightly oversized, and requires a special tap with a standard size drill bit. Installing a 1/8" npt heli coil will remove less material than going up to 1/4" npt.

I used a ton of them in a past life. Mostly machine threads, not many npt.

there is something about you need to use a taper reamer in there if you want it to end up tapered too.

the insert can unscrew from the hole but in something delicate like that it might be the better option

HomerJSmith

If you are going to tap it, use threading oil on the tap and don't force the tap. If you run into resistance while tapping, back it out a couple of threads and re- tap. Go slowly with plenty of cutting oil.

Giants9890

jesmed1 said:

I would try what Mad Dog said before trying more extreme measures. You may be able to get it to seal by doing as he says without any further drilling or tapping. "Quick wick" may not be readily available to you, but you can get it on Amazon: https://www.amazon.com/Loctite-442-35082-Length-Sealing-Off-White/dp/B000ORA0MM/ref=sr_1_1?crid=2HALOURWKP1NQ&keywords=plumbing+quick+wick&qid=1696433628&sprefix=plumbing+quick+wick,aps,93&sr=8-1 And there are many types of pipe dope, but I've had good success with this: https://www.amazon.com/Rectorseal-23631-Brush-Thread-Sealant/dp/B0002YPAFY/ref=sr_1_1_sspa?crid=1WGRNSH9WTW7A&keywords=rectorseal+t-2&qid=1696434105&sprefix=rectorseal+t-2,aps,104&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1 Apply both to a 1/8" black iron nipple (with coupling for the vent) from Home Depot as Mad Dog said. You may find that's enough to seal it.

Thank you so much. Have my Amazon cart ready to go but concerned this female coupler isn’t the right material. Thoughts please?

jesmed1

@Giants9890 No, not aluminum for the coupling! You want iron. Let me find a link for you.

Here ya go:

https://www.amazon.com/Anvil-8700132957-Malleable-Fitting-Coupling/dp/B0058DHZSY/ref=sr_1_4?crid=9EI2OV3W6H1Q&keywords=1/8+black+iron+coupler&qid=1696469789&sprefix=1/8+black+iron+coupler,aps,90&sr=8-4&th=1

Giants9890

Hi All, images of the old radiator valve, newly purchased nipple, and all items purchased. The nipple will not screw in to the hole. It appears the old valve lost its threads inside of the radiator. What can I do now? Thank you for helping me through this as this bedroom turns into an oven. 

ChrisJ

Giants9890 said:

Hi All, images of the old radiator valve, newly purchased nipple, and all items purchased. The nipple will not screw in to the hole. It appears the old valve lost its threads inside of the radiator. What can I do now? Thank you for helping me through this as this bedroom turns into an oven. 

Please see my post from October 4th.
That will still fix the problem.

Buy an 1/8" NPT tap and a handle that works with it. I would not use oil with the tap.

OldawgBryant

Tap it (I have done my share in the past. Oil or not, but go slow and stay straight. If you feel too much resistance, then back it out and start again. The last thing you want to do is snap off the tap in the hole. You might want to practice on another piece of metal by drilling the required hole so you get the feel of it. I usually use the oil, as there won't be so much to mess-up the system.

Giants9890

Problem officially solved. Thank you everyone! I tapped the thread and was able to get a varivalve in with pipe sealing cord wrapped around it.