Copper pipe soldering: Flux burns the moment I apply heat

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FreeLander

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Oh yeah, make sure you have something to catch the dripping flux.
Nothing like drippy flux landing on your arms. That's why I solder the furthest fitting first and work my way back to me.
Can you please have a look at my reply to John? I'd appreciate your input. Here
 

John Gayewski

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Solder gets sucked towards the heat.
This is a common misnomer. Without flux solder doesn't go anywhere. Really the solder follows the flux. You can get any copper as hot as you want the solder won't follow the heat.

The liquid solder is pulled in through capillary action aided by the wet flux. Made possible by heating the solder to a liquid.
Thanks, John! this is very helpful. Maybe you can help me decide which is better, soldering or brazing, for my application. The reason I'm learning this is that I bought a heat exchanger that has a copper manifold, and I want to solder it to a CopperToCPVC adaptor. One guy on YouTube was struggling with this as too much heat deformed the CPVC end of the copper fitting. Please watch this and tell me what would you do? Would you instead braze it with a Harris 15% to minimize heat exposure? That's what I was thinking, at least. Would love to hear what you think.

You cannot braze a cpvc adapter. Brazing happens at 840 degrees f minimum. Soldering can go around 390 degrees f with thre right solder
 
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FreeLander

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This is a common misnomer. Without flux solder doesn't go anywhere. Really the solder follows the flux. You can get any copper as hot as you want the solder won't follow the heat.

The liquid solder is pulled in through capillary action aided by the wet flux. Made possible by heating the solder to a liquid.

You cannot braze a cpvc adapter. Brazing happens at 840 degrees f minimum. Soldering can go around 250 degrees f with thre right solder
I guess the golden question is: What is the right solder? I ordered this: https://www.amazon.com/dp/B000BQOAEK?psc=1&ref=ppx_yo2ov_dt_b_product_details

Do you think it'll do for my application?
 

LLigetfa

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I've never worked with a copper-to-CPVC adapter but probably you could thread on a metal nipple to act as a heat sink to keep it from deforming. Extra heat sink could be had by wrapping the vulnerable section with a wet rag.
 

JohnCT

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Thanks, John! this is very helpful. Maybe you can help me decide which is better, soldering or brazing, for my application. The reason I'm learning this is that I bought a heat exchanger that has a copper manifold, and I want to solder it to a CopperToCPVC adaptor. One guy on YouTube was struggling with this as too much heat deformed the CPVC end of the copper fitting. Please watch this and tell me what would you do? Would you instead braze it with a Harris 15% to minimize heat exposure? That's what I was thinking, at least. Would love to hear what you think.


Don't braze! Soldering is so much easier and requires less heat.

Regarding the CPVC adapter, I'm afraid I have no experience with this (I'm an amateur as well), but you are smart to hone your skills on test plumbing.

The video you linked makes sense: you want to keep the temperature of the cpvc end low. Have you considered using a threaded adapter?


https://d3501hjdis3g5w.cloudfront.net/images/products/zoom/brcpm100-nl-3.jpg

John
 

John Gayewski

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I guess the golden question is: What is the right solder? I ordered this: https://www.amazon.com/dp/B000BQOAEK?psc=1&ref=ppx_yo2ov_dt_b_product_details

Do you think it'll do for my application?
Yes this will work. I personally like to use Bridget solder because has a very low melt point and a wider paste range than most. All of the other guys at work like canfield so I end up using that a lot it's pretty good stuff, but it's melt point is so high it's kind of annoying.
 

LLigetfa

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Have you considered using a threaded adapter?
DOH! I just realized the flaw in my suggestion to screw in a nipple to form a heat sink as the CPVC fitting would be slip, not threaded. If you sweat on a copper transition to female thread, you could than transition a CPVC male thread to slip adapter.
 

FreeLander

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This shouldn't be that difficult. Being where you are, I'm not familiar with your solder and flux brands, so there may be an issue with your supplies. Perhaps you're doing this correctly and your flux is just burning at a temperature lower than your solder needs to flow. Asking a local plumbing supply where you are may clear up any issue with your material.

Regarding cleaning, do not skimp on this stage. Everything you have read about cleaning pipe is not an exaggeration. Your pipe must be thoroughly abraded with sandpaper, a stiff wire brush, or steel wool so the copper shines like gold - inside and out before applying flux.

Here in the States, most amateurs use a typical propane torch which works fine for 1/2" and 3/4" pipes. For larger pipes, MAPP gas is an option as well, but no matter what heat source you are using, it's very important not to scorch the pipe and flux, or the joints will need to be disassembled and *re-cleaned* with abrasives.

This is a very short video that shows what properly heated pipes and solder flow looks like. You don't need to wipe after you make your joint - that's pretty much for show.


Good luck!

John
Thanks, John. I came to realize that Propane and Mapp is not commercially available where I'm from. Only Butane. Could this be the problem?
 

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Thanks, John. I came to realize that Propane and Mapp is not commercially available where I'm from. Only Butane. Could this be the problem?
The type of gas doesn't matter. Butane just burns hot so you don't need to heat it as long. Your over heating it.

Heating can be done with gas or electric resistance. Gas doesn't matter is can be any kind some are just easier for beginners.
 

FreeLander

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The type of gas doesn't matter. Butane just burns hot so you don't need to heat it as long. Your over heating it.

Heating can be done with gas or electric resistance. Gas doesn't matter is can be any kind some are just easier for beginners.
Alright then. Could it be possible that the flux I'm using can't stand the heat and just burns too fast before the solder melts? I made sure to go slow and low with the torch, but the moment the solder melts, the flux is long gone. I tried re-fluxing while joins are in, it catches up just a little bit, then solder starts dropping not melting to the joint. Could this be the reason? Some flux was not meant for copper soldering, maybe? I even tried a thinner solder but it was the same. Melts and drops it does not stick to the joint.
 

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Alright then. Could it be possible that the flux I'm using can't stand the heat and just burns too fast before the solder melts? I made sure to go slow and low with the torch, but the moment the solder melts, the flux is long gone. I tried re-fluxing while joins are in, it catches up just a little bit, then solder starts dropping not melting to the joint. Could this be the reason? Some flux was not meant for copper soldering, maybe? I even tried a thinner solder but it was the same. Melts and drops it does not stick to the joint.
It could be the wrong flux. There are all different kinds of flux. Yours being completely foreign to me, I'd have no idea. I use the ones from plumbing supply stores.
 

LLigetfa

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then solder starts dropping not melting to the joint.
It sounds like you are heating the solder wire with the flame. Keep the flame away from the solder wire. It is only the heated copper that should melt the solder. Heat only the fitting, not the copper pipe.

From the pictures you posted, you are clearly overheating the copper with way too large of a flame applied for too long. I also see no evidence of the joint having been thoroughly cleaned.
 

FreeLander

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It sounds like you are heating the solder wire with the flame. Keep the flame away from the solder wire. It is only the heated copper that should melt the solder. Heat only the fitting, not the copper pipe.

From the pictures you posted, you are clearly overheating the copper with way too large of a flame applied for too long. I also see no evidence of the joint having been thoroughly cleaned.
Thanks. The cleaning part I can do better at, but for the too-large flame, do you recommend I get another torch with a smaller opening?
 

Weekend Handyman

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Thanks. The cleaning part I can do better at, but for the too-large flame, do you recommend I get another torch with a smaller opening?
I am not a plumber or pro. If you want to make your life easier buy a Bernzomatic TS4000 torch. The trigger start is great. As a non-pro, I like to use Oatey Safe Flo solder with Oatey tinning flux. I have never had a leaky joint.
 

FreeLander

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Turn your flame down, it's way to high, then go back and forth over the pipe and fitting with the flame and every few seconds touch the joint with the solder, when it melts to the touch remove the flame and only apply the flame to the pipe when the solder stops melting. after the joint is soldered wait for the solder joint to go from shiny to dull then wipe it down rigorously with a cotton cloth.
Wear cotton gloves when soldering so you don't burn your hands on the hot pipe.
Clean pipe and fitting by sanding or brushing.
Flux on inside of fitting and outside of pipe.
Apply heat to fitting and pipe, touching every so often to see if the fitting is hot enough to take solder.

Let set until cool, then wipe the fitting with a rag.
I like to have a spray bottle handy, and gloves. Hot copper will give you a nasty burn if you touch it too soon.
This shouldn't be that difficult. Being where you are, I'm not familiar with your solder and flux brands, so there may be an issue with your supplies. Perhaps you're doing this correctly and your flux is just burning at a temperature lower than your solder needs to flow. Asking a local plumbing supply where you are may clear up any issue with your material.

Regarding cleaning, do not skimp on this stage. Everything you have read about cleaning pipe is not an exaggeration. Your pipe must be thoroughly abraded with sandpaper, a stiff wire brush, or steel wool so the copper shines like gold - inside and out before applying flux.

Here in the States, most amateurs use a typical propane torch which works fine for 1/2" and 3/4" pipes. For larger pipes, MAPP gas is an option as well, but no matter what heat source you are using, it's very important not to scorch the pipe and flux, or the joints will need to be disassembled and *re-cleaned* with abrasives.

This is a very short video that shows what properly heated pipes and solder flow looks like. You don't need to wipe after you make your joint - that's pretty much for show.


Good luck!

John
Brazing requires a lot more heat than soldering.

I'd like to thank you all for your help. Turns out the issue was with my torch. It was way overpowered. I replaced it with this one and threw extra effort with the cleaning and the solder melted like butter and found its way around the pipe. May not look pretty but it is leak-proof. I'd appreciate your feedback. Thanks again.

The crème brûlée torch is ideal for caramelizing sugar atop creme brulee, glazing a baked ham, searing a steak, roasting bell peppers, melting cheese, and toasting breadcrumbs. It is also useful for lighting your fireplace, candles, or cigars, for hobbies, arts and crafts projects, jewelry making, welding, for multiple camping applications, dabs, and much more.



Screen Shot 2022-04-12 at 1.18.04 AM.png
IMG_4987.JPG
 

FreeLander

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It's not bad, may need more solder. apply solder to the joint until some drips out of the joint then your sure the joint is full.
Alright, but when I apply solder to the front of the joint, do I need to apply to the back too? Or does it find its way all around?
 
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