Whats trick to soldering copper pipe?

topic posted Mon, December 19, 2005 - 2:27 PM by  Dano
OK.. so, it seems easy enough... clean copper pipe with emory paper,
Flux pipe and fitting generously (with the right kind of flux), insert pipe into fitting, heat joint with torch (I have a MAPP gass torch) until "perfect temperature" and apply solder to the joint watching it suck up into the joint sealing it perfectly. RIGHT?!?! thats what is supposed to happen...

So how com I either overheat the pipe and evaporate the flux or underheat it and cause gloops of stiff solder to go nowhere?
Any one have any good tips or references to how to solder copper pipe?
Oh and bonus points.. how to get solder to run "uphill" when you have a joint facing that direction... Should the side the solder is suppoesd to run (fitting side) be heated a bit hotter than the other (side pipe side)?

Thinking seriuously about CPVC..

posted by:
SF Bay Area
  • Don't worry about burning up the flux. Make sure that there is no water in the pipe, that will turn to steam and you will wind up with pinholes in your fitting. (I learned the hard way)

    Just keep even heat on both ends, and then pull the fire away, and test by pushing the solder onto the joint, if it melts go around it until the solder is evenly around the joint. Don't worry about drips either. let cool, and pressure test for leaks.
  • It is alright if you let the flux boil. it will still work. Make sure you are sanding or brushing the inside of the fiting too. Tarnished spots cause bad solder adhesion. For uphill, design your process early enough that you can pre asemble pipes that are in anoying spots, and make connections where it is simple.

    Consider using pecks tube instead of copper. More environmentally friendly, lasts longer, and installs with ring clamps.
  • Unsu...
    Heat from below, the area with the greatest mass and away from the joint (typically on the piece/fitting that the pipe is fitted into - NOT the pipe itself)...

    apply solder from above - the heat will draw the solder in...

    it takes a while to learn how not to apply too much which looks "sloppy" (some plumbers even wipe the joint with a wet cloth just after removing the flame).

    A plastic scatcher works better than emery paper unless the copper is really black and use a pipe fitting brush on the inside of the fitting.

    Copper is perhaps the best way to go - we have lines at the hospital that are 100 years old and show no signs of aging.
  • OK... good info so far... So the torch should be Off the pipe when you apply solder...

    What happens when you pressure test and find leaks? what is teh remedy? I imagine you have to cut off teh offending section and redo? is there a less destructive way to reseal?? My big fear is that I'll get this project done and pressurize the pipes only to find a bazillion leaks and thus destroy much $$ in pipe and fittings as well as the many braincells from the resulting binge drinking that will follow.

    I'm "really" thinking about CPVC for this project. BTW I'm putting a loop of pipe from water heater to hot-tub heat exchanger and back to hot water heater return. I know copper is best but now that I think about it I don't see why I couldn't just go with cpvc as it would cost less than half and take less than 1/4 the time. to install.

    • Unsu...
      No you are still applying heat with torch in one hand and solder with the other, once the solder has been sucked up into the joint and bubbles slightly remove heat - should be no leaks...

      if there are - drain it down, reheat and reapply solder...

      lots of apprentice plumbers have done it.

      CPVC is junk - google it.
      • Unsu...
        I'm new to this skill too, but found (at Home Depot) fittings that already have the solder in them, and they work great. Looks like they have a little flange, which is really just a ring of solder. So, apply the flux, fit the pieces together and heat away. Only thing is that both ends of the fitting have to be ready to go or you'll melt the solder out of the other end. I'm sure some of the experts could give you more advice on these fittings - but I've had no troubles with them yet on a shower refit.
        • Unsu...
          According to a plumber I used to work with, back in the days when pipe making tollerances weren't so great it was common practice to "tin" (apply solder) all pipes and fittings before piecing it together for finish solder.
          • Unsu...
            Though the picture quality isn't that great, I've added a shot of the work I did with the fittings I meantioned (above) to my profile - take a peak if you wish. If I had a better shot I'd add it to the tribe photos.

          • Unsu...
            I used to tin my joints all the time - I had a old book.
            When I finally joind the 20th century I realized that tinning caused more trouble than not.
            Tinning. I didn't think anyone even knew the expression anymore.
            • Unsu...
              I call it tinning with soldering wire and pre-coating the ends with solder... but I think I picked the expression up from my 65-year-old dad who was a landlord and dragged me along to help with all the painting and repairs as a kid.
            • Unsu...
              I am sure that the term "tinning" is still used in electronics and jewelry circles, because they probably still do it when soldering.

              In electronics or electrical soldering, you pre-tin a surface that you are intending to solder something to by applying a coat of solder. In particular, you would do this to wires that you want to join. Once both wires have been tinned, they will solder together very easily.
    • One of the advantages of copper is that leaks can be fixed by simply reworking the offending solder joint. Just give it some more flux and some more solder. In rework, it sometimes helps to "hot flux" a joint. That is, you put some heat on the joint, brush on some flux, then more heat and solder.

      In terms of pressure testing, the "pro" approach is air testing. You need to make up a test rig using a pressure gauge and a "snifter valve" on a tee fitting. The "snifter" is similar to the air fitting on a pneumatic tire. Hook up your test rig to your piping, pressurize to say 100 psi with a bicycle pump, and check for leaks... No need to drain down piping for rework .
  • Unsu...
    Any kind of soldering, whether copper pipes, electrical and electronics, or jewelry, is a skill that takes practice to perfect.

    But if you follow the tips already given and practice on a few scrap pieces before you tackle the actual job, you'll get the hang of it.
  • Practice makes perfect, but I saw that Home Depot is now selling copper fittings that have the solder already in them.

    They are made by Watts and are widely available.

    This looks like a good option for you so you can get your project done and move forward.
  • it is very important to thourghly clean both the pipe and the fiting. (I use steal wool). When you are heating up the joint, watch the flame color on the pipe. When it has a green color, apply the solder to the pipe oppisite of where the flame is on the joint. The solder will be sucked up into the joint and spread around the pipe. It will even flow uphill. You know you have applied enough solder when you see solder starting to drip out. remove heat and solder imedeatly and let joint cool.
    • Unsu...
      Which brings up another good point...

      the flame is hottest where it comes to a blue point - that is the part of the flame you want to expose the pipe to.
      • Unsu...
        Yah but this guy is using MAPP. That is way hot. He can be very sloppy about the heat zone 'cause the only thing he needs to worry over is too much heat.
        • perhaps this "mapp" torch is too hot? I know that in electrical/electronic soldering, it is a mistake to use one of those big soldering 150 watt guns for most jobs, since too much heat will damage the connected components, melt the circuit board, cause solder to melt too readily too close to the iron but not further away (depending on the heat-transfer properties of the joint's metal), etc. For most electrical jobs, a cheap 30-40 watt pencil soldering iron is actually better. It takes a while to 'pump' sufficient heat calories into the joint before applied solder will melt and flow by itself (from the heat of the now-hot component, not from the heat of the iron), but you can do so in a more controlled, even manner.

          I imagine a similar thing might be true for soldering pipes-- what you want is sufficient EVENLY distributed heat occuring on all metal throughout the whole joint, suitable for melting solder anywhere within and around the joint, not 2000 degress on one side and 400 on the other.
  • I love this tribe. You get what is sorely missing in most hardware stores... real DIY experience and a range of opinions. I'd say 80 to 90% of the info in the responses is right on and very helpful. At some of my local hardware stores (especially the big box stores) I'd ask for advice just to hear the half-assed answer and make sure NOT to do what they told me. I found that about 50% to 60% of the time they knew much less than I did about the product or process in question. about 20% of the time they were just plain wrong or just scratched their head and gave me that "You can't get there from here" look.

    Thanks Folks.
  • Unsu...
    I'm going to ignore everything already said 'cause it's way too much to read just now.

    Look get these tools:
    Wire pipe cleaners -- the inside and outside ones that fit the pipe sizes you have.

    A big tub of flux

    Some thick leather patches

    A file: #2 mill is fine

    A pipe cutter - you really do get what you pay for - get a good one.

    Hangar Strapping

    You already have a torch and a hammer.

    1. Measure and cut the pipe assembly to size,
    2. Hang it in place,
    3. Examine your layout.
    4. Clean the pipe parts with the wire brushes
    5. apply flux to all parts to be soldered inside and out - no need to overdo it just be thourough.
    6. Re-assemble the layout with the flux.
    7. Go from one end to the other of your layout to the other heating the joint (not the area around it ) just enough so the solder melts on contact and flows into the joint. NOTE: While you are melting the solder into the joint the heats is being lose so you'll likely have to apply some heat as you sweat.
    8. DON'T touch the joint till the solder is fairly well set.
    9. Just as the solder is about to harden use one of those leather wipes to clean the excess solder off. If you prefer not to touch it, then don't. It’ll only leave a drip of solder.
    10. move on to the next joint. REPEAT.
    11. When done and the solder is cool Clean the joints with anything Use 409 or whatever to get the residue of the flux off the pipes as it will cause ugly discoloration and corrosion.
    12. Take a picture and post it in your profile. Go ahead and have a gloat.
    • Thanks Cliff...

      Sounds good, very concise summation...

      But ya know...
      I thinking I might just buy a box of Milkbones and have that guys dog do it.

      Who can pass up cheap labor!
      • the trick for getting the solder to suck up into the joint is heating the fitting (NOT the pipe) an inch or so away from the mouth where the pipe enters the fitting.
        By heating up the outside of the fitting a little ways away from the opening, the solder you apply gets drawn up into the joint through convection.

        *make sure you apply flux to both the outside end of the pipe and to the inside of the fitting

        *apply enough flux to the pipe so that some of it is still visible when the pipe is fully embedded in the fitting.

        *do not touch the flux after applying. oils from your skin will prevent the solder from taking.

        *obviously make sure the surfaces are totally clean that you are applying flux to.

        *just heat the outside of the fitting until the solder melts into the joint. Keep adding solder, trying to get it on all sides of the joint. When the solder starts to drip OUT of the joint, it usually, but not always, means that the joint is already full of solder and that you are done.

        *after soldering it is good to clean the joints with soap and water, leftover flux can corrode the copper, and that is often why you see old copper pipes with crusty white and green spots around the joints.

        *let copper to brass connections cool on their own, but copper to copper connections can be cooled right away with water from a spray bottle.

        I know I've repeated some of the advice from others but whatever.

        Good luck!
        • Don't heat the pipe, only heat the fitting. there is no reason to heat the pipe.
          • OK... as a wrap up to this project... I ended up making two short legs of copper pipe into and out of the heat exchanger on the hot tub (that soldering went fine thanks for the help!) I did end up going with CPVC though for the supply and return legs from hot water to the hot tub heat exchanger... I thought I'd let you all know why (so you can see that I didn't just wimp out)

            After discussing and thinking the project over I went with CPVC over copper for one reason only. The others (cost and ease of installation turned out to be fringe benefits)

            Reason 1. Thermal conductivity. As this is a double closed loop hot tub heat exchanger, I wanted to lose as little heat as possible between the water heater and the heat exchanger (a 50 foot trip one way).... Yes I could insulate the copper but there is still a good deal of heat the copper wicks before the water gets to the exchanger and insulation also costs more. CPVC has so little conductivity that the pipe is barely warm to the touch when the heat exchanger is running.

            I will be repiping the entire house water supply later on (with copper) so all this discussion was definately not in vain for me. and I did have to solder several copper joints and fittings anyway.

            Thanks again all! Oh and there is a finished picture in the photo gallery of the tub (no deck yet)
            • Unsu...
              CPVC joints don't hold well with heat and pressure...

              cut 3 inch wide strips of reflectix to wrap the pipe with overlap by half while wrapping, duct tape or better yet aluminized tape for the joints on the wrap - best insulator around.

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