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PVC pipe is a great material for making things.  If you ever need to bend the pipe, here's how to do it.

The trick is to fill it with sand before heating the plastic and bending it.   Normally, the pipe would pinch closed in areas where it is bent, but the sand prevents that.  When the heat forming is finished, you just drain out the sand. 

 
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Step 1: Safety while heating PVC

Picture of Safety while heating PVC
We love plastics for what they do for us, but plastic manufacture and decay tend to pollute the environment and negatively affect our health.

Vinyl Chloride, one of the components of PVC, is carcinogenic. When it is locked up in the polymer, however, it is much safer to be around. In my years of experience working with PVC, I have not noticed any adverse effects on my health from being around it.

Always work in areas with good ventilation. If you do get caught in a cloud of smoke, hold your breath and move to clean air.

When heating PVC with a gas stove or propane torch, try not to let it burn. Smoke from burning PVC is bad. With experience one burns it less and less. Don't panic the first time you do burn some. It scorches, but doesn't immediately burst into flame. Move the material away from the flame and try again. Don't breathe the smoke. Smoke avoidance comes naturally for most people.

While heating PVC over a gas flame, keep the plastic an appropriate distance from the flame to avoid scorching the surface before the inside can warm up. It takes time for heat to travel to the center of the material being heated.

Keep the plastic moving, and keep an eye on the state of the plastic. When heated, the PVC material is flexible, like leather. Beyond this stage, you risk scorching it.

A word from James, the plastic engineer -- "Just a word of warning, PVC can handle some high heats but if it catches fire, you wont be able to put it out, it does not need oxygen to burn so don't do this inside".

I do work inside, but my house is made of cement and has good ventilation. MAKE SURE THAT YOU HAVE GOOD VENTILATION. PLAY WITH FIRE -- CAREFULLY.
A few people have asked if you can do this without a stove. YES! But this might not be what you were thinking:
I have done this with GREAT success using sand and a toaster oven. I put the sand on a tray in the oven and heated it to about 212˚-280˚F, then quickly and carefully (with a funnel) pour the sand into a capped piece of pvc. At this point I just held the pipe vertically with one hand (at the open end) and sort of "wiggled" it back and forth until it began acting like a cooked noodle. Pretty soon it's soft and bendy and you can do what you like with it! The sand keeps it from collapsing and provides the heat. I was consistently bending 2" radius curves with no problems!

On a different note you have a quote that says "...it does not need oxygen to burn so don't do this inside". I find that hard to believe since fire is an oxidation reaction and you can not have fire without an oxidizer (oxygen). 6th grade teaches you the three things needed for combustion: heat, fuel and oxygen. So I don't see how it could "burn" without oxygen. Am I missing something chemically here?
Epic instructable! i never would have thought you would have to put SAND in it. Thanks!
Thanks for the instructable, i will use this to make the sump return for my marine tank!
AntMan2323 years ago
I don't like to put a damper on things, but as far as i know, when you heat PVC you get chlorine gas, which is poisonous. I just thought i'd let you know, but its probably too late...!
I'm not sure, but pvc may also give off cyanide gas when overheated. I'm sure that many plastics do give off this gas and it is a very real danger to inhale it. Any super glue that contains cyanoacrylate will certainly give off cyanide gas when burned and many plastics manufacturing processes include stuff like this in their products. PLEASE be careful when heating plastics and always have a lot of ventilation - use a fan if you have one even outside, no need to take chances with your life over a piece of plastic!
Thinkenstein (author)  jack85591 year ago
Check it out, if you are not sure, and let us know. Poly-Vinyl-Chloride doesn't sound like cyanide to me.

I agree that there are no known health benefits to breathing burning plastic. The art, not a difficult one to learn, is to not burn the plastic when you soften it. Yes, good ventilation is always important.
You would need a lot of direct heat to form toxic gas, I have bent lots of PVC with no problems at all. The bending temperature is about 100 to150°C and it takes a temperature of about 390°C or more to char PVC.

If forced to burn PVC will not produce chlorine but will emit dense acrid fumes containing noxious and toxic compounds including carbon monoxide, hydrogen chloride and possibly dioxins.
However PVC will not burn on its own, it needs continuous applied heat to char it.
Thinkenstein (author)  AntMan2323 years ago
Well, I know how chlorine smells and I have never smelled chlorine while heat forming PVC. Of course that is below burning temperature. If you burn PVC, yes, you get some nasty fumes. The fumes don't smell like chlorine to me, but they probably contain chlorine. With fumes that smell so bad, I never hang around to analyze the aroma in detail. Anyway, and I swear I'm not lying, I'm still alive!
If you insist, i'm a bit doubtful about the last comment, but i'd better take your word for it!
Your 'ible made me think. In highschool we never used heat to bend pvc pipes, for our installations we used something that you could just stick into the pipe and then bend it using your own force. Then when you were done you'd simply pull it out and the pipe would remain undamaged but bent in a nice curve. I think I have one of those things lieing in my garage. I'll check tonight and see if my memory isn't betraying me...

If it works like I remember I'll post a picture and maybe make an 'ible of my own about it.
Thinkenstein (author)  MichelMoermans4 years ago
I imagine you are thinking of another material.  If you bend PVC cold, it tends to spring back into its original shape. 

Anyway, whatever you remember seems new to me, and I'd like to know what it is. 
no, i know what hes talking about, and hes right.
its like a long spring, one of those pull versions, it fits really nice inside, and it doesnt require alot of force!
Yep, that's right. It's some sort of a spring.

I asked my dad about it and he says that it works with all "normal" PVC pipe of normal diameter.

Just stick the spring in there and bend using your hands. I can't find the spring in the garage right now but if I can't find it in the morning I'll search for a picture on google :)
http://www.youtube.com/watch?v=PFB2-8gWzl0

There ya go, it was quickly found. This is what we used in school. A spring that bends the pvc pipe cold without compromising the integrity or durability of the pvc pipe also the spring is the same diameter as the innerhole so while bending the hole won't get smaller.

This video explains how it works and how less time consuming it is.
Thinkenstein (author)  MichelMoermans4 years ago
I never would have believed it possible, but I saw the video.  Pipe Viper.  I'm going to have to send for one of those.  Thanks.
You're welcome :)

According to me it has been around for atleast 4-5 years since I came in to contact with it when I was 14.

That's why it suprised me nobody here seemed to realize you could bend pvc cold. Well this is were instructables is for gaining knowledge and using it to fit your needs  :D
how does it work?
www.youtube.com/watch

This video should give you a pretty clear picture.

But it's just sticking the spring in. Look were you want to bend your pipe. And bend it with your hands until you have the shape you want. Then you just pull the spring out and your done :D It does require the use of some force but if a 14 year old can handle it I'm pretty sure everyone here can too.
I mean, what are the mechanics of it?
The spring supports the pipe wall and prevents it buckling.
I have bending springs for copper pipe but had not realised that it would work for PVC pipe without heat.
looks alot like a weakened version of a garage door spring
The Pipe Viper is a pretty amazing concept!
Funk_D4 years ago
This is awesome! Just this morning I was trying to think of a way to bend some PCV I have to make a bike rack so I didn't have to go buy 90 degree joints! Thank you!

Also, do you think this method would work with copper piping? I need to bend some into a radiator shape but I can't figure out how.
Copper pipe can be bent cold using a bending spring. These are only three or four pounds each but you do need the right size for the pipe.
If you had a spring the right size then you could use it with heat for bending PVC pipe.
Thinkenstein (author)  Funk_D4 years ago
I think copper pipe has been bent cold with sand inside.  Pack it tight and give it a try. 
 If you get ductile copper tubing, it is bendable without heat.  The straight stuff is not so bendy though, and is prone to cracking and creasing instead of bending clean.
jcksparr0w2 years ago
to improve this instructable, you can also heat you PVC with a heat gun(used in art for embossing paper or other materials). Much less chance of fire, much safer, and works about as well. Good idea to post this though.
Thinkenstein (author)  jcksparr0w2 years ago
A heat gun is fine. Not everybody has a heat gun, though. Propane torches and gas stoves are more common.

You can play with fire and not get burned. You just have to be careful. Keep work moving to avoid hot spots, and at an appropriate distance from the flame.
yutzwagon3 years ago
This looks pretty cool. I wanted to make a boffer kukri, so I think this should work well. Thanks a lot!
Thinkenstein (author)  yutzwagon3 years ago
You're welcome. Apparently, a kukri is a curved knife. I don't understand the reasoning behind shaping a knife like that. If I recall correctly, boffers used to be sort of foam swords people could boff each other with, without hurting each other. If I was crossing a boffer with a kukri, I'm not sure what I would get. So how does bending PVC pipe work into making a boffer kukri?
the drop in a kukri's blade is to help chopping power and there has been stories of Gurkha kukri's chopping a man from skull to pelvis in a single stroke
Thinkenstein (author)  asda12462 years ago
I'll keep that in mind next time I have a similar task.
I think a Kukri is more of an axe hatchet knife combo. The curved edge makes it easier to cut.
I suspect the PVC forms the solid core that the foam is then attached to.
Thinkenstein (author)  ingvar3 years ago
Thanks. It seems like it could still hurt, though. I don't think the old boffers had any solid cores. They were just thicker at the handle and more flexible at the tip. Maybe there was something solid in the handle, though.
All the boffers I've built in the past had a solid core, but with a decent amount of foam everywhere except the handle (and usually using an all-foam cross-piece).
I made a falcata (a sword with a blade shape similar to that of kukri's) and it works fine as a boffer.
Ryutso2 years ago
Is there a way to reduce the wrinkling on the inside of the curve?
Phil B2 years ago
Bending PVC and then cutting it in half along its length is a reasonable way to save a bunch of money on making your own lightweight and very durable bicycle fenders. Get some 1/8 inch rod to bend and attach for supports.
ilpug2 years ago
amazing. after the PVC is heated and bent, does it retain it's pressure rating?
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