How to Bend Copper Pipe and Tubing Without Crushing It




About: I'm passionate about combining engineering and sustainability through DIY technology. I'm a mechanical engineering student at Olin College and currently building things at TechShop in San Francisco as an int...
I recently made a copper tubing coil to use in a solar-powered water-boiler and learned the right way and the wrong way to bend copper tubing.  The tubing is easy to bend when making large-radius curves, but is likely to kink or crush when trying to make smaller-radius bends.  I learned that I could avoid those problems by filling the tube with salt before bending.

Here's what I used.
  • .25 inch Copper pipe.  5 feet long
  • 1/4 cup of Salt.  (Fine, dry Sand would also work)
  • Tape
  • Funnel (or makeshift funnel)
  • Vice
  • Hammer
  • Hard Cylindrical Objects of various diameters.  I used a 3" diameter steel pipe and a 1.5" diameter socket-wrench socket.

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Step 1: Fill It With Salt

  1. Your tubing probably came as a coil, so straighten it out to begin.  Use a flat surface like a table and roll the coil while holding one end on the table.
  2. Stand the tube upright and use some tape to cover the bottom hole.
  3. Use a funnel or other tool to pour the salt into the tube.  Fill it all the way to the top.
  4. Help the salt settle by tapping the tube on the ground.
  5. Refill with salt until it can't settle any more.
  6. Cover the top hole with tape.
Now you're ready to bend.

Step 2: Bend Using a Cylindrical Object

  1. Begin by bending your tubing into a much bigger circle than you want to end up with.  
  2. Clamp your cylindrical object in the vice and, by hand, gently wrap the big coils down to coil around the cilinder.  Sometimes a twisting motion can be useful, turning one end of your coil clockwise and the other counter-clockwise.
  3. Tap the tubing with a hammer (while it's on your cylinder) to help it reach an oval-shaped cross-section.  This lets it stay happy even when making tight coils.
  4. Continue the process with smaller and smaller cylinders until you are at the size you desire.
Take the tape off the ends and shake out all the salt!
You're done!

For more advice on bending tubing, check out this article.

If you're curious about the Solar Parabolic Water Heater, check out the instructable.

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    60 Discussions


    26 days ago

    I own a carpet cleaning business and use truckmounted equipment in my cleaning trucks my catalitic heat exchanger is leaking can you help me with spooling a new coil.


    10 months ago on Step 2

    Very useful tutorial. Thank you.
    I only have one question.
    Can I use this method to create an internal coil ? I mean what are the limitation to the value of the bending radius ?
    Thank you.


    3 years ago

    WATER! it can't compress. ice shrinks when melted; bending it heats it and melts it. use WATER!

    2 replies

    Reply 1 year ago

    Nope. You are missing why this is done.

    Water expands when frozen, and you don’t need to seal the pipe.

    Adding the soap drops the freezing point, and adds a slippier interface between it and the tube if a small layer does melt.


    Reply 2 years ago

    To take advantage of how water cannot compress, you would need to fill the tube with water and have absolutely no air in the tube. You would then also have to seal the tube such that absolutely no water leaks out while you are bending and shaping the tube. If so much as a drop comes out, then any and all advantages of using water would have been lost because an air bubble would replace that drop. In the end, even if you do get it right, this method would prove far more complicated than just using fine sand and tape. Filling the pipe with salt or sand is such pure genius that I am somewhat disappointed that I did not think about it... I think that these are some of the ideas that you get only after you have already started working with what you have...


    Question 1 year ago on Introduction

    How long does it take ypu to do a 3.5m lenght of 12.5cm tickness and what will the cost therof work out on?


    7 years ago on Introduction

    Even better, for even tighter results, fill the tbe with low-melting-point alloy. We use a material that melts at 80 C, and then steam it out hot after forming

    11 replies

    Reply 7 years ago on Introduction

    Brass trumpets are bent by filling the tube with soapy water, then freezing them. After forming, the water melts at room temperature.


    Reply 2 years ago

    I assume the soap makes bubbles that allow for the flexibility that pure ice would not allow.


    Reply 7 years ago on Introduction

    Only saw it on an episode of "How it's Made", but I would think that is for lubrication purposes.


    Reply 7 years ago on Introduction

    Trouble with ice is its crystalline, and cracks, leaving voids that tend to collapse the pipe. It might work in brass, in the very large relative curves in trumpets, but we make very fine coils


    Reply 7 years ago on Introduction

    Just keep in mind that most of these low temp alloys contain a fair amount of lead and cadmium, possibly with other toxic metals, so if this is for use to heat drinking water, those alloys should be avoided. Then again, with a heat exchange system, it may not matter,

    Once again i find you helping with your most-excellent advice Steve !

    GREAT Tip with the Low-Melt Alloy !

    Im very Curious though, whats the name of the low melt alloy you use and is it easily acquirable ?!?

    many many thanks too !!


    thanks steve, most-highly-appreciated !!!

    even-better as im in the UK !!!

    but i only found a company from the website and all the links on it are broken and dont work, would you be able to tell me if this it the place or post the correct website please please ??

    once more, many thanks again !


    6 years ago on Step 2

    Tubing for musical instruments traditionally was bent by either being filled with lead or frozen soapy water. The companies involved do not release the type of dish soap or the amount used in proportion to the water in the mix.
    The important part is mostly that the mixture be well frozen.
    These days the best method is to have a die built that holds the pipe and hydraulic pressure is used to force the tube to perfectly fill the void.

    1 reply

    Reply 2 years ago

    The term "the best method" would have to be used with a pinch of salt, there, as any method's evaluation should take: cost, ease of use and ease of access into account before we can crown such method as being the best... This could be said to be "the most accurate" method or something, but not "the best" unfortunately, as it requires specialised tooling and machinery, etc. etc which the above method does not.