Introduction: How to Bend PVC & Make Incredible Shapes

Picture of How to Bend PVC & Make Incredible Shapes

I was recently working on a project where I needed to bend pvc pipes into smooth, round shapes. After some trial and error I found an easy way to get great results.

Step 1: Testing

Picture of Testing

First of all, cut your pipe to size, I used a variation of different sized pipes for this test. I found that if you heat up the pipe only with a heat gun from the outside it's hard to get a smooth curve, and you easily get kinks. Plus, you can only heat up a small section at a time. What I needed to do was find a way to heat up the pipe from the inside out.

Step 2: Tape the End

Picture of Tape the End

Duck tape on the end makes a nice block and then I measured out how much sand fit inside the pipe. I used regular sand that I had on hand and then I heat it up in a pot until it was pretty hot.

Step 3: Filling the Pipe

Picture of Filling the Pipe

I filled the pipe almost to the top, maybe with two inch empty space, and taped it shut.

Let the pipe rest for a few minutes to heat up thoroughly. Then with gloved hands you can start bending and manipulating the pipes. You can either do this freehand, or bend around something, like a jig or something round to get a precise shape.

Step 4: Different Pipes

Picture of Different Pipes

Once I held the shape for a little while, I poured out the sand, and there you go!

I tried this technique with a couple of different sized pipes. The larger pipes took longer to heat up and were a little harder to bend, however it's still possible to get slight curves. The thinner pipes however become very maluable and easy to bend into all sorts of crazy shapes!

Step 5: Conclusion - Watch the Video

For a much better perspective, make sure to watch the video that goes over the steps, and to see how easily the different pipes bend.

Comments

Haunted Spider made it! (author)2017-10-31

I used a very similar technique last Christmas for a chandelier at my Church. I used sand as well and heated it up in an oven at 500 degrees. That seems to be the right temp to get it to bend the PVC properly. I had several tins of sand going as I had multiple pieces to bend in a row. The jigs definitely help to shape the pieces over and over the same.

WillisJ1 (author)Haunted Spider2017-11-13

That's pretty awesome! I wonder what it would look like with balloons covering it?

DustBunny (author)Haunted Spider2017-11-02

Amazing!

rdölz (author)2017-11-04

Anyone attempting this should be aware that, when heated, PVC may release CARCINOGENIC VAPORS. So always be in a well ventelated area and always wear suitable breathing protection

tinaciousz (author)2017-11-03

You're so great <3 Thanks for always sharing your wisdom with us!

HjoacoM (author)2017-11-03

Excellent work!

bpark1000 (author)2017-11-02

I use a propane torch, applied carefully, for gradual bends on heavy-walled pipe, for making underground irrigation sleeves into which the flexible line is inserted . It takes about 5 minutes of carefully moving flame to do it. This allows me to selectively heat only the parts to be bent. You could integrate this heating scheme with your hot sand method to heat the pipe from both inside and outside. You could also dump out and reheat the sand multiple times.

truesprocket (author)2017-11-01

The sand also keeps the pipe from folding. The fuller the better

KenM17 (author)2017-11-01

Fill the pipe with BBs if sand residue is a proble,

iceng (author)2017-11-01

+1

iceng (author)iceng2017-11-01

Voted for you !

GTO3x2 (author)2017-10-30

Duct tape - It came from using it on furnace ductwork.

MillerI (author)GTO3x22017-11-01

Seconded! Also, malleable: a term meaning the ability to change shapes with ease.

jexy9 (author)2017-10-30

Great one. Thanks. The pipe will try to maintain its round shape due to the fact that a circle has the greatest area for a given perimeter, therefore the pipe will maintain its internal volume and its round cross section. The technique of filling a copper pipe with sand before bending, to avoid kinks, has been used for ever. Of course being as I am I had to figure out optimum temp for the sand. A quick search found

https://www.plastikcity.co.uk/useful-stuff/materia...

which indicated that the best moulding temp for PVC was between 20 and 60C depending on grade. 60C is about the upper limit for being able to hold comfortably - and that only for a short time.

Maybe the problem of heat penetration of thicker pipe could be overcome by not only filling the pipe with hot sand but also burying it in hot sand as well. Would obviously need more sand and some sort of trough but may be worth a try.

erniewallbanger (author)jexy92017-10-31

Jexy, I have to correct you there. The mold temperature is the setting for heating up the mould when injection molding. It simply does not relate to the plastic properties of PVC

The charts also gives the MELT temperature. This is the setting for the process of the injection molding. This temperature will produce a melt viscocity enabling a melt flow into the mold. This would be called the molding temperature.

Your point on the thickness issue is spot on! Plastics conduct heat poorly compared to metals so it will take a while for the heat to reach the outside, if ever!

I think there are some instructables on Injection Molding, have a look if you are interested,,,

Best regards, Ernie W.

jexy9 (author)erniewallbanger2017-10-31

aha thanks for clearing that up Ernie. I still wonder then what the optimum temp would be for this process. Maybe a bit of trial and error. Although the melt temp gives the temp for injection moulding, I was under the impression PVC pipe was extruded. Imagine that if the PVC pipe is heated too high, it would lose integrity and tear or rupture. Searching further for properties it seems that the loss of stiffness is fairly linear (and slow) until it gets to about 55C where it stars to lose stiffness more quickly. From 80 to 90C it again seems loss is linear but quite rapid. So perhaps the ideal temp range is somewhere there.

erniewallbanger (author)jexy92017-11-01

I would go for trial guided by error! You are right when looking att properties, this will give you a guide but practical result is what counts. Just for bending, anything that looks ok is ok. As long as it keeps its circular shape and bends with little resistance

But for a pressurized och chemical system I never would use bending, cold or heated, as there is a risk of damaging the properties of the tube. Then it is pipe and fittings.

As pointed out here, never use an open flame!

PVC can be extruded as well as molded. Just different grades with differnt additives.

Good luck to You, learning by way of doing!

Ernie

WinsionL (author)2017-10-31

Interesting , and helpful , thanks girl !

eddand (author)2017-10-31

we needed to bend abt 150 pcs of 3/4 inch sched 40 pvc into large sweeping bends. we cut the top off an electric water heater propped it at abt 45 degrees and filled it with water. we had to ocassionally turn the heater off because as the water reached boiling the pvc became to soft and would flatten when bent. we put a piece of wire mesh in the heater protecting the hearing unit from contact with the pvc. we could keep abt 8 to 10 pieces soaking in the heat at the rate we were able to bend them if the water is to hot you must bend faster or cool the water down.

hammockhiker (author)2017-10-29

Electricians use this tool: http://www.greenlee.com/catalog/Bending/PVC-BENDERS

pdavis19 (author)hammockhiker2017-10-30

True, but I think her solution is more flexible and allows for sizes that the Greenlee's don't. I'm a big Greenlee fan, but they're not cheap: $400+ for the 1/2" to 2" bender, $900+ for the 4" and $1400+ for the 6" puts them out of reach of most hobbyists.

DavidG809 (author)pdavis192017-10-30

Do you think a heat blanket could be used to bend pvc or acrylic sheets?

DennisT33 (author)DavidG8092017-10-30

For acrylic sheet people use strip heaters to soften an area of sheet clamped to a bench, and then bend it much like a sheet metal brake. You can use a propane torch but it's easy to singe it and the area of bending is not as confined.

This trick for PVC pipe is pretty clever, and is likely the only approach that doesn't risk kinking the tube. I have deformed PVC pipe with a torch (i.e. to pinch a constriction near the end) but it wouldn't suffice to bend a tube like this.

DavidG809 (author)DennisT332017-10-31

As I understand it. Strip heaters are only good in making sharp angles
What I meant was to use a blanket for curving sheets
Ie make a wood jig in the curvebyou want. Lay an open. Blanket over it then the acrylic sheet on that

I never bent plastics before I’m just spitballing ideas

Chipper Bert (author)DennisT332017-10-30

Electricians use a bending spring without any heat but you need some practice get an even curve. Also without heat the curve relaxes somewhat so you have to over-bend. The spring can also get stuck in complex bends so has its limitations. Very fiddly so the hot sand method is about as nifty as it gets other than as someone else has suggested, to use common salt instead of the sand.

Syncubus (author)DavidG8092017-10-30

Unlikely on the heat blanket. PVC's melting temperature is around 160 °C (320 °F), which would be dangerously hot for an electric blanket/heating pad (which are normally intended for direct skin contact).

https://en.wikipedia.org/wiki/Polyvinyl_chloride

ed-romes (author)hammockhiker2017-10-30

As an electrician that tool was used to make small offset bends to allow for a wall mounted circuit box to be connected to the pipe that's mounted to the wall but for the bends called sweeps they come pregame from the factory !! To make the bends shown here having sand in the pipe is a must even with the greenlee hot bender without the sand one size of the pipe can kink or suck in while the other size stresses out and becomes to thin !!

Oncer (author)2017-10-31

Voted for! But how hot is "pretty hot"? Within the range say of a sugar thermometer? It's just I can see me doing this and ending up with a puddle of PVC with extra sand!

Blackanga (author)2017-10-30

Very good idea. It has been used for ages to bend various metal pipes (not only copper - steel too, although the much higher temperature is required). However, for PVC, I would suggest using a table salt instead. It's cheap enough and it has been used as a poor man room heater (in the pot/pan over a stove) for ages. It heats up nicely and additionally, it will not leave any deposits inside the pipe, that can't be dissolved and washed off after.

Chipper Bert (author)Blackanga2017-10-30

The salt is a grand idea except when you are getting creative on a Sunday morning and there is not much salt in the cupboard and the shops are closed.

To get any residue out an ordinary vacation cleaner works pretty well. If you want to really be sure, tie a small rag onto the end of some thin fishing line and suck it through with the vacuum. Then tie a sliver of sponge to the line and pull it through. Repeat until you are happy.

You can do really long lengths this way. I wired up my garden for lighting and used HDPE pipe as a sleeve. I laid about 60m with multiple curves around ponds and flower beds and had no problem sucking the fishing line through.

jemuel sands (author)2017-10-30

I used a hair dryer as I didn't have a proper tool. It worked really well!

azapplewhite (author)2017-10-30

Very clever and simple with fantastic results. Nice job, thanks for posting.

ooohlaa (author)2017-10-29

i love this, but wondering what kind of uses to put it to, artistically its really wonderful but nothing comes to mind except lamp base and floor lamp base, picture/mirror frame, chandelier? None of which do I need, anybody?

chris.gaines.71 (author)ooohlaa2017-10-30

I've been doing this for parrot perches, swings and toys ... easy clean in the dishwasher!

Syncubus (author)ooohlaa2017-10-30

Tool holders, towel racks, grab bars, truck rails, bumpers or landing gear for RC cars/quadcopters, custom hula hoops, marble machine pipes, Archimedes screw pumps, etc., ad nauseum...

shrivver (author)ooohlaa2017-10-30

I was thinking it would be great for plumbing hard to reach areas! so much better than all those couplers!

skylane (author)shrivver2017-10-30

It absolutely can be used for plumbing. You can make your own coupling on one end of PVC by heating it with a heat gun. The pipe to be inserted needs to be beveled. Force the cool beveled piece into the heated pipe about an inch or so, let cool then remove. Now glue as usual.

I'd be cautious about using this technique for actual "pressurized water plumbing".

As you can see from the pictures, sand gets trapped in the plastic - which may come out and clog your fixtures.

More importantly, there will be some "thin" spots in the tubing after bending which might compromise the integritiy of the pipe for pressurized water.

pdavis19 (author)ooohlaa2017-10-30

As shrivver mentioned, piping in certain locations, you could do custom bends without having to use joint pieces (which have fixed diameters). PVC is frequently used for artistic stuff as well, and so it would handy for that, obviously.

Poopontherug (author)2017-10-30

Very clever. Gòd job thinking out of the box, Bill.

louis.m (author)2017-10-30

I'm a retired electrician/plumber and learned this "Hot Sand" trick
more than fifty years ago at school. Nice to see it's still in use.

As
I remember it also worked well on lead pipes, and even makes the
bending of other materials like copper and aluminium easier (even
square tubes). Part of the trick is keeping the tube in such position
that sand can flow into any open space in the bend caused by the bending.

jpfalt (author)2017-10-30

Could you steam the pipe from the interior with a wallpaper steamer as heat source?

Syncubus (author)jpfalt2017-10-30

Unlikely on steam bending. PVC melting temperature is around 160 °C (320 °F). Steam isn't going to get much hotter than 100 °C (220 °F) without being under pressure.

Jim L. (author)Syncubus2017-10-30

I've seen someone use a pressure cooker to render the desired flow and heat. Bring the temp up slowly until you get the appropriate flow/temp.

jimvandamme (author)2017-10-30

I needed a shallow bend in 3 inch drain pipe once, so I heated it up over the gas stove. Don't expect to make pretzels with that technique.

tschuld (author)2017-10-30

the problem with this is getting consistent temperatures, I've found that using boiling water (100C) works and leaves no residue. takes some more prep but seems to give better results. add a spring just under the inside diameter of the pvc to avoid kinks

FerretPD (author)2017-10-30

Umm...this really *IS* a great idea (no...*REALLY*!)...but can we *please* get some specific temperature/time data?

At what temp is PVC malleable?

At what point does it begin to melt?

Those are critical values that would make your Instructable *MUCH* more useful!

dewey302 (author)2017-10-30

Wow. I've been trying for years to figure out how to make smooth, permanent bends in PVC. I'll be trying this out for sure. Thanks for sharing your ingenious solution.

Chuckwilcox (author)2017-10-30

Great idea, thanks for sharing. Always good to keep these ideas in the back of your mind, might come in very useful one day.

C4mpi59 (author)2017-10-28

Great idea! I was thinking if i taped an empty pipe(meaning filled with air) and then I would use a heat gun on it, would it work? Air inside would heat up and hopefully stay inside the pipe, so it should work maybe worse than sand or duct tape would puff up (hot air highers its volume).

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