fizzling and dripping at union between radiator and radiator valve

bkselly

Union video - may have to click on the pause button on the bottom left as it won't autoplay

After I moved into this house, I had noticed that there was always a little bit of steam coming out at the union

I recently decided to repaint my room and detached the radiator from the valve, thinking that this would be a good opportunity to apply some pipe dough and reattach to try to fix the steam leak

Now I notice that there is fizzling and some water leakage as seen in linked video

I tried to tighten the union as much as I could, but I feel like any further will break the pipe going into the floor

What are some things I could to stop the leak? I'd say it's about 50 mL leakage over 12 hours. I am still new to steam heat so I may have missed something obvious

pecmsg

Is the radiator lined up perfectly with the fitting?

Are the faces of the union clean and smooth?

Put some high temp grease AKA neversieze on the back of the nut where it rides and a little on the threads. Even a small amount on the mating surfaces.

Waher

Clean the mating surfaces with clean cotton rag. Clean the threads. Apply pipe dope or Blue Monster tape on the threads. Line up the radiator as straight as possible with the mating surfaces and press them together as snugly as you can. Tighten the nut slowly by hand and use a wrench with three points of contact (to avoid ovalizing the nut) to tighten until snug. If it still leaks after that both the spud into the radiator and the valve itself will have to be replaced.

Usually what happens is the mating surfaces weren't snug enough, rust/grit got into the void over time and either rust jacked or eroded the material until it no longer sealed. Someone well meaning might have attempted to tighten the nut in the past without using a wrench properly and ovalized the nut making things worse.

I'd try again and if it doesn't seal you'll need to proceed with replacement.

Jamie Hall

Whatever you do, make sure that the mating surfaces of the union are absolutely clean first, and free of scratches or nicks. Do NOT use an abrasive -- even emery cloth -- on them. Then, if you like, add a very thin -- and I do mean thin -- smear of Neverseize on one face only. Line up the radiator spud with the valve horinzontally and vertically and angularly -- unions will not take up misalignment.

Then push the thing together and hand tighten the union nut. No dope -- or perhaps a tiny amount -- is needed. The nut does not do the sealing! Then no more than half to three quarters of a turn with a wrench. If that doesn't work, double check for cleanliness on the mating surfaces -- but you may be out of luck.

bkselly

I had applied a bit of pipe dope on the face of the union as seen in this YouTube video at the 7:25 min mark

How to Replace a Steam Radiator

In terms of cleaning the mating surfaces, should I use something like a microfiber cloth?

What is the benefit of neverseize over pipe dope for the inside face coming from supply valve?

Long Beach Ed

Alignment is key. Do as Jamie says. Look at it from all angles. Make sure the radiator's not cocking the pipe back and that the riser is perpendicular through the floor. In stubborn cases, I've used Teflon pipe dope on the face of the union but it really shouldn't be necessary. Tightness won't make it better; alignment will.

Jamie Hall

The problem with pipe dope on the mating faces is really quite simple. It won't squeeze all the way around and across the face to make a seal when you pull the union together. When you put dope on a thread, it smears itself around and becomes continuous. On a union, there is no smearing, and if there is even the slightest gap it will happily leak. Guys like @Long Beach Ed can get away with it. Sometimes. Ordinary mortals, not so much.

bkselly

Apparently none of my local hardware stores have never-seize

I found this online: Loctite 495556 Silver-Grade Anti-Seize Lubricant Tube, 1-oz.

Would this work?

Waher

The anti-seize/pipe dope/Teflon tape is ONLY used at the threads to keep the nut from getting stuck. It doesn't have be anti-seize, it just has to be something to keep the union from welding itself together with corrosion.

bkselly

Thank you all - cleaning the mating surfaces and reseating resulted in a very minimal drip. Probably the valve and spud need to be replaced to get rid of all leakage, but now it is barely noticeable