Bending PVC Pipe - Just Because You Can

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Introduction: Bending PVC Pipe - Just Because You Can

Have you ever found yourself putting in that new sprinkler system for your garden and right in the middle of the project discovered that you are out of 45 degree fittings?  With this simple technique, you can heat bend custom fittings in any kind of PVC pipe.

The secret to the process is using a controlled heat source and spreading it out. In a word keep: it moving, keep it rotating. (OK, that was more than "a" word)

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Step 1: Heating the Pipe

PVC pipe is created by a process called extrusion.Extruded products are all around you: Spagetti, macaroni, aluminum door thresholds, vinyl window frames, plastic bags ... even plastic water bottles (which start as extrusions before they are blow molded) ... all these are extruded.  In the case of PVC pipe, chips (or beads) of rigid PVC plastic are heated up to a molten state and forced through a hole correspondng to the shape desired - in this case, a pipe.  As the pipe is extruded, it is held in a straight line until it cools into a solid length of pipe. 

PVC is a thermoplastic - which means that it becomes soft when heat is applied.  You can use this little tidbit of knowledge to heat and re-form the pipe to a new shape without compromising its physical properties ... if you are patient.

The best tool for heating the pipe is a heat gun - available for around $25 from your local hardware big box or online (search: 1500 watt dual temperature heat gun).  You can also take your piece of pipe into the kitchen and use your stove top - just make sure your wife isn't home.  What doesn't work so well is a propane (or MAPP) torch as the heat is too concentrated and charring the PVC is highly likely. Save the torch for making your PVC diggerydoo ... but that's another instructible.

The key to the technique is constant movement - move the PVC pipe or the heat source back and forth over a 12" or so area and keep the pipe rotating all the while.  After 3 or 4 minutes, the piece of pipe will start to sag.  Keep it moving and rotating and begin bending it while rotating it - all the while keeping the heat on. 

Step 2: Finishing the Bend

Once the PVC pipe is good and soft, lay it down on a flat suface and bend it while rotating (or rolling) it.  Do not bend it quickly or stop rotating too soon or the pipe will kink.  Once the bend is the correct angle, hold it while it cools.   As long as you don't overheat it or kink it, it'll hold pressure just like a straight pipe. 

Remember: your heat gun is also your friend when running PVC pipe (or conduit) and you have to make that ~12 degree angle in order to get it into that next fitting - even if the pipe is already in the trench.  Just remember to keep the heat source moving - but please don't try drying your hair with it.. 

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    45 Discussions

    I've heard of filling the pipe with dry sand to keep it from kinking. I've also seen where you can heat and bell out the end of the pipe so you don't need a coupler.

    9 replies

    Cold bending PVC can work - especially in smaller sizes - 1/2" is easy. I challenge anyone to try to cold bend anything larger than 1". And ... if the pipe has become brittle with age, it's going to snap regardless of how small it is.

    I had an exterior electrical J-box made-up with 6 PVC conduits w/ wires run and everything that got rejected in an inspection ... supposedly because there was a stand-pipe too close in front of it. I put a canvas tarp over the whole thing (to help contain the heat) and got out my heat gun. It took about 15 minutes to heat up all 6 conduits but once everything was nice and hot, I was able to rotate the entire J-box a full 90 degees, conduits still in place. Another 5 minutes to cool it off and it looked perfect (and got passed in the next inspection).

    Use care if cold bending pvc. Building a small greenhouse I had a 10 foot section snap. No harm but scared the smarts into me. Next bend was covered with heavy tarp.

    Just a hint. When cold bending 10 foot sections in summer, let sections rest on concrete or asphalt under black plastic in sun for a couple hours. Makes a big difference.

    My scout troop used the hot sand method to do snoeshoes a while back. The process was essentially to cook the sand until it was fairly hot, then pour it all into a cut-to-length PVC pipe. Then two people with gloves would bend the frame into a wooden jig, and hit it with a heat gun if needed. They actually came out really well. I have about 25 sets of snowshoe frames (unfinished) hanging in the garage... 0_o

    The end effect looks like this: http://i.ytimg.com/vi/3RSIzMTfX7A/0.jpg
    (bindings are made of rubber tire innertubes from old tractor tires with some bolts for traction. I'm sure theres an instructable out there for doing them if you looked)

    That sounds like a fantastic idea. Is that photo from a tutorial or instructable somewhere? I'd love to read about it, especially the construction of the jig and the bindings.

    My troop did the same thing. We made a couple and they turned out great. I was really impressed with how well the snowshoes ended up. Definitely one of my favorite projects we did

    Hey!
    I remember years ago I saw an article about a man that was using pvc pipe to make "futuristic" lamps (it was an ooooold article). Anyway, what he did was take 1" to 1-1/2" pvc pipe, cut it to longer than he thought he would need, and push a cap (not glued) on the end. Then he would heat up a disposable casserole dish full of sand in his oven (don't remember the temp-sorry) and then would pour the sand into the pipe. As I recall, after a few minutes the pipe would soften and then he could bend it without it kinking, When it was in the shape he wanted he would run cold water over the pipe and into the sand to cool everything off and stiffen it up again. The rest was just regular lamp building stuff. But I always thought this would be a handy thing to try someday!! I've used a heat gun to soften pvc to make holsters for various tools myself. Just don't char it because it does release chlorine gas which is really nasty stuff. Kill you quick. Your mileage may vary.

    All of these methods sound pretty cool, but why doesn't someone simple make a heated, expandable coil that you could insert into the pipe, turn it on, and while it's heated properly, bend to a desired shape?

    3 replies

    The reason is that you don't want to heat the entire pipe. Since you can't usually control where the heat is in a coil it's not very effective at the job.

    Another possibility that we could try would be to take the inner coil idea, and use induction from a ring outside the tube heat the pipe that way.

    There is a commercial device for heating pipes - costs $200+ depending upon size and length. Called PVCBendit, available at a website of the same name.

    I think PVC fumes are toxic. Wear a mask

    I work at a place that makes pvc conduit, and the way we make bends is to insert a rubber hose after rotating the pipe under a heater, pressurize the hose so it won't collapse and bend the pipe and clamp it down to a jig. After that, we submerse the pipe (and jig) with the hose inside it into water to re-harden it so it will retain its shape. After a few minutes, remove the jig from the water, take the pipe off, let the prssure off the hose and remove it and you're done.

    Standard pvc pipe can also be heated in oil until it reaches around 375 dgrees F and insert a larger diameter pipe, rod, or other tool to make the bell end for a pipe then cool with water so it will retain the shape. I did this where I used to work because all the hardware stores were closed and we had a pipe that HAD to be repaired and we had no couplings....

    1 reply