Difficult Connection to Hot-Water Radiator


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Old 10-17-14, 03:59 AM
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Difficult Connection to Hot-Water Radiator

In a way, this is a general plumbing problem. But it is also specific to radiators, so I hope this is the right place to post.

The flow-control valve failed on one of my old cast-iron hot water radiators. I got a new valve from my big-box store, with 1/2 inch threads for both inlet (internal thread) and outlet (external thread): 1/2 in. Hot-Water Radiator Angle Valve

What makes this difficult (for me, anyway) is that the piping comes through quite close-fitting holes in the flooring. For this reason, I'm not able to rotate the valve about a vertical axis (the valve outlet would hit the coupling to the radiator).

Also, I'm not able to rotate the tube coming up through the floor, because the supply must reach the radiator in a tight space between the floorboards and the thick foundation wall.

So I don't have a way to install an externally-threaded riser coming up through the floor, and then to spin the valve onto it.

What I tried (with misgivings) was to tightly thread a 1/2" threaded-to-copper coupling onto the bottom of the valve, and then to sweat this whole assembly onto the copper tube rising through the floor (with the valve positioned to mate to the radiator).

Normally, I am careful to avoid sweating with such a large heat sink as this valve (the valve body is probably 5 times as massive as the old valve that died). I heated the coupling as much as I could with a propane torch -- solder melted quickly on touching the coupling -- but when I touched the solder to the joint, it didn't flow smoothly the way I always hope to see.

Sure enough, the joint has a trickle leak.

Please, any suggestions?

Would it make sense to try the same stunt again (soldering to the coupling while it's attached to the valve body), using a hotter torch (whatever passes for MAPP nowadays)?

Is there any kind of fully flexible connection (like the metal braided hose used for water supply lines) that is appropriate and reliable for a hot-water heating system?

Is there some simple trick I missed?

As I began writing this, it occurred to me that a "simple" way out would be to significantly enlarge one the floor holes for the radiator piping, enabling me to solder the coupling by itself and then "spin" the valve onto it. But for several reasons, I would prefer not do this surgery on the floor, if there's another way.

Thanks for your time and suggestions!
 
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Old 10-17-14, 07:38 AM
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Hi George,

I'm trying to envision what you are describing...

Perhaps it would help if you could post a few pictures of what you are dealing with? Might help us come up with some ideas...
 
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Old 10-19-14, 08:00 PM
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OK, I took photos.

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My initial question, was rooted in my ignorance. [Not very important, but after I broke down the installation, I realized that (a) there IS enough clearance for me to tighten the valve on the upright (by rotating it about its vertical axis), and (b) although the solder joint didn't look very good, it was solid -- the leakage was through the threads between the valve and the sweat adapter.]

But I still have a problem, and basically it's the same problem. I remade the feed line and the upright, this time WITHOUT having the valve in place when I soldered the threaded adapter.

I tried to do everything very carefully, but ended up with the same kind of leakage (not even a trickle, but seepage) via the threaded connection.

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Basically, I am very comfortable and confident with soldering, but my luck with threaded connections has not been so good!

In the close-up photo, you can see a little droplet of the leakage (on the right), and also that there's maybe 1 and 1/2 turns of thread still showing on the sweat adapter.

Of course, I can try tightening the valve onto the threaded sweat adapter -- but my only option is to tighten it by 360 degrees. The torque was quite high to get the valve where it sits now, and I worry whether I can make another full turn without getting stuck or damaging something.

I would very much welcome any voice of experience here!

Would it make sense to try a few more wraps of Teflon tape, or is that a fool's errand?

Should it be feasible for me to tighten the connection another full turn?

Is there anything else I can do to -- perhaps some kind of compound to seal up the threads?

Thanks for your attention and suggestions!
 
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Old 10-20-14, 03:45 AM
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Would it make sense to try a few more wraps of Teflon tape, or is that a fool's errand?

Should it be feasible for me to tighten the connection another full turn?
Best to remove it and re-tape. Also use Teflon paste on top of the tape...
 
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Old 10-20-14, 08:46 AM
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Don't put any tape or dope on the first 2-3 threads of the male adapter. These threads need to meet with the other threads METAL TO METAL.

Any more than 2 wraps of teflon tape is TOO MUCH. It appears that you have have several too many wraps.
 
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Old 10-20-14, 03:21 PM
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It's easy to underestimate the torque needed for threaded connections. The one pix shows a threaded copper adapter that is leaking. Because copper is ductile, more torque is needed than with steel pipe and fittings. You'll have to torque it some more - which means breaking a soldered connection. When you redo it, consider adding a union so you can re-torque without breaking the connection.

The purpose of teflon tape or paste is to act as a lubricant so that you can get greater metal-to-metal interference with less torque. Not as a sealant. Tape or pipe dope also helps loosen threaded joints when necessary.
 
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Old 10-20-14, 03:51 PM
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Because copper is ductile
This is also one reason that you may now not be able to stop the leak. The threads may be deformed to the point where you can't get a seal at the first 2-3 threads and will always have that 'spiral leak path'.

You may end up having to replace the adapter.

Too much teflon tape is probably the single biggest mistake that even 'experienced' plumbers make. It will actually prevent one from getting the joint tight enough! With too much tape, you tighten a valve or fitting to where it 'feels' tight enough, and yet ...drip...drip...drip... maybe not right away, but give it a few days/weeks... drip...drip...drip...

Do an experiment yourself if you want confirmation of this. Put six wraps of teflon tape on a male fitting and thread it into a female part. Do this in a vice on a bench... tighten it until you think it's 'tight enough'. Leave it sit a couple days and come back with a wrench and tighten it again. You'll be surprised to find it's loosey goosey.

This is because the pressure compresses the tape. The tape 'flows'. The joint loosens. You probably never had that metal to metal seal that you should have had the first time you tightened it.

Ever wonder how all those threaded joints that the dead men made didn't leak?
 
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Old 10-20-14, 04:09 PM
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Ever wonder how all those threaded joints that the dead men made didn't leak?
That was before Teflon and Teflon tape. And the dead men could tell by feel how much torque was necessary - it takes a while for us DIYers to learn it. It was before threaded copper adapters, too.

In the old days, they used some type of pipe dope - not sure what it was for sure, but possibly petroleum based? That old dope hardened over time, and can be a bear to loosen joints after several decades. For that, Teflon is better.

Teflon tape is tempting to apply too much of - since it's mistakenly thought to be a sealant, not a lubricant. And, the tape, or at least the remaining shreds and crumbs, are a solid, it interferes with metal-to-metal interference. Since pipe dope, either the old stuff or the newer Teflon kind is a viscous liquid, it's difficult to apply too much.

With those copper adapters, I've found just more torque is the ticket. But without a union in the line, trial and error may involve breaking soldered connections.
 
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Old 10-20-14, 04:15 PM
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With those copper adapters, I've found just more torque is the ticket.
But threading into brass I have cracked many brass fittings in my day.... You cannot go to town on that joint....
 
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Old 10-20-14, 04:43 PM
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In the old days, they used some type of pipe dope
I like that black tarry stuff for heating pipe threaded applications. I think the stuff they use now is a different formulation that doesn't eventually harden. Alcohol is a solvent. I believe that 'Permatex' was one of the makers of the old pipe dope. People started using it as a 'gasket' and it worked well... so they renamed it!

Note that they do actually call this a 'sealant' and not a 'lubricant'.

15510 - Hercules 15510 - Grrip Thread Sealant - 1/4 pt.

I like the idea of a union myself, but I don't see enough room to install one without burning down the house.

I have cracked many brass fittings in my day....
Even brass onto copper? You BRUTE!
 
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Old 10-20-14, 04:56 PM
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Even brass onto copper? You BRUTE!
No just the brass fitting... I cracked copper once in 30 yrs...
 
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Old 10-22-14, 01:33 PM
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Gentlemen,

I deeply appreciate the time you have taken to help with my little problem! I'm renewing a lavatory, and the toilet will go close beside the radiator -- access would be very difficult with the toilet in place, so I feel pressed to get this thing resolved before installing the fixtures.

I hadn't thought of using a union. In this situation, there is no room for one either above or below the floorboards, but I'll keep it mind for the next time.

Trooper, I used narrow tape, so I went around perhaps 3 times. But I didn't overlap the turns much, so at any point there would be 1 or 2 thicknesses of tape.

Nobody addressed this directly, but my intuition is that it may not be possible to tighten this joint another 360 degrees, and if I got only part way around (without breaking anything) I would have further deformed the threads, leaving me with an even worse problem.
________________________

In doing some other searching online, I got the impression that (a) lots of people have problems with lengthwise seepage along the threads of brass NPT joints, and (b) there is lots of conflicting advice about how to solve this

Draining and refilling the hydronic loop is slow and inconvenient (I don't have a proper drain in my basement, and must pump the water out). I've already done it twice, and would be happy to make the next time the final one.

At this stage, I have discovered that Oatey makes a product called FASTape which apparently is significantly thicker than typical Teflon tape. Also, my Home Depot stocks Hercules Megaloc thread sealant compound, described thus:

Does not harden, crack or become brittle
Joints can be disassembled without damage to pipe, fittings, or threads years after the joint was made
Performs over a temperature range of -50F to +400F

My inclination is to go with one of these.
 
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Old 10-22-14, 02:14 PM
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Why to you have to tighten it a whole 360 deg? The leak is where the copper adapter threads into the valve, right?

Do you have access to the pipe from the basement? You could add a union there? Or replace the copper nipple with a black steel pipe - they are much less susceptible of leaking than threaded copper fittings.
 
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Old 10-22-14, 02:24 PM
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In doing some other searching online, I got the impression that (a) lots of people have problems with lengthwise seepage along the threads of brass NPT joints, and (b) there is lots of conflicting advice about how to solve this
Tape alone will bind.... Must use paste.........

Oatey makes a product called FASTape which apparently is significantly thicker than typical Teflon tape.
No!!!!!!!!

Also, my Home Depot stocks Hercules Megaloc thread sealant compound, described thus:
Probably not needed... Real tuff... teflon based.... Is all I use. 30 plus years...

Hercules 8 oz. Real-Tuff Thread Sealant-156202 at The Home Depot
 
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Old 10-22-14, 03:06 PM
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@gilmorrie:

I tried to explain before (a drawing would be better, but it takes me too much time): 6" below the floorboards is the top of a 2' stone foundation wall. (The house is civil-war era.) My nearest practical point of under-floor access is more than 2' (horizontally) from the radiator.

So there is no practical way to "turn" things from underneath.

@lawrosa:

I'll buy me some Real-Tuff this evening! You are generous in sharing your professional experience.

I shall let you all know how it goes!
 

Last edited by George Antrobus; 10-22-14 at 03:22 PM.
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Old 10-22-14, 04:17 PM
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OK, I think I visualize it. What about this: cut out the copper and replace with a black steel nipple going vertically from the new valve. Put a steel el at the bottom end of the nipple, and then shoot another steel nipple horizontally, and go from there. The copper pipe is of modern vintage, so it must have been installed somehow. Black steel fittings are available at any decent hardware store.

If this doesn't make any sense, then please post a sketch of the arrangement.
 
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Old 10-23-14, 02:04 AM
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WITH A NAME LIKE REAL-TUFF ...

... it's got to be good.

Real-Tuff not only kicks ass, it also takes names.

I will bare-knuckle box any 3 guys who diss Real-Tuff.

Real-Tuff can file your tax returns, and remove viruses from your computer.

OK, maybe I'm going a little too far ... but everyone who was kind enough to respond to my problem will have guessed, that I now have a leak-free connection.
________________________

Here is how it went:

After draining my heating loop for the third time, I disconnected the valve first from the cast-iron radiator (which frees the valve to rotate) and then unscrewed the valve from the vertical copper feed tube with its 1/2" brass NPT adapter.

I then cleaned the shreds of Teflon tape from the adapter.

Meaning no disrespect to Lawrosa, I decided to use the paste alone (no tape). It's my first time using the product, and I wanted to try following the manufacturer's directions. My understanding of the concept of this product, is that it acts both as a sealant (mechanically blocking leakage paths along the length of cut threads due to thread imperfections), and a lubricant.

I spread the paste around the circumference of the NPT adapter, and then used a brush-handle to clear excess so it was leveled with the peaks of the threads (even with that done, there is a lot more paste than necessary, which squeezes out during tightening).

As I threaded the valve onto the (now-gooped) male adapter, the lubricant effect of the paste was obvious: I could easily turn it most of the way using finger pressure.

I wrenched the valve to its necessary orientation (lined up with the radiator, about one turn before the end of the threads) with little torque, but this didn't worry me. The product is spec'd for liquids up to 2000 PSI, and under normal operating conditions my first-floor radiators run at about 10 PSI.

I wiped up the excess paste with a paper towel.

Recharged the loop, bled air from radiators ... no seepage.
________________________

Had I known this before, my first attempt would have worked fine, and I would have saved two drain/recharge cycles, a remaking of the soldered tube assembly from the basement to the male adapter, and the re-assembly I just described.
________________________

I've used Teflon tape several times over the years without problems, but some of that was on other surfaces (for example, plated threads on a shower head). But I've also had several tiny leaks with brass NPT connections. Most of the brass NPT threads I see look kind of rough; perhaps the dimensional control and surface smoothness just aren't good enough for Teflon tape to reliably do the job.

Now, I know what to do

PS You guys rule
 
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Old 10-23-14, 04:29 AM
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Meaning no disrespect to Lawrosa, I decided to use the paste alone (no tape).
LOL... I dont use tape all the time either... he he...



but everyone who was kind enough to respond to my problem will have guessed, that I now have a leak-free connection.

Thats great news.... Good job..
 
 

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