Bend PVC Pipe

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Introduction: Bend PVC Pipe

About: I'm a refugee from Los Angeles, living in backwoods Puerto Rico for about 35 years now and loving it. I built my own home from discarded nylon fishnet and cement.

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. 

Step 1: 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.

Step 2: Fill the Pipe With Sand

Cover one end of the pipe with masking tape to hold the sand in.   Fill the pipe with sand, tapping the taped end of the pipe on the ground to compact the sand inside.  When the pipe is full of compacted sand, tape over the top end.  You are ready to heat and bend.

Step 3: Heating and Bending

I use a gas stove for heating and bending sections of pipe. 

Hold the pipe from both ends.  Keep the pipe moving back and forth over the flame, rotating the pipe all the while so that the area to be bent is evenly heated. 

Keep the pipe at a reasonable distance from the flame to keep from burning it.  Heat penetrates slowly through the plastic.  Be patient.  Haste can result in burnt plastic.  Don't try to heat it too fast.

When the plastic softens up some, the pipe begins to sag from its own weight and the weight of the sand inside it.  It gets leathery.

At this point, turn off the stove and bend the pipe into the shape you want.  Do it on the floor, if you want to keep it all in one plane. 

Step 4: Some Finished Shapes

These are a few bent pieces of pipe.  The ends of the pipe are still taped. 

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1 Questions

do you think a square form could be pushed into the hot pipe to form a square pvc tube? i want to make a rectangle tube from 4" pvc drain pipe (the 1/8" kind). i may have to reheat a few times. i,m concerned that the whole piece may compress trying to push the form into the hot pipe. thanks

Mike

Much easier to buy the square PVC drain pipe that is available than to try to make it.

3 more answers

thanks for the comments. both are great ideas. I,m looking to make a rc pontoon boat similar to a craigcat basically 2 surfboard shaped pontoons. i will be heating the pipe in a electric oven and sliding a top and bottom form into the pipe as the pipe starts to sag, then wedging middle wedges in to get the final shape from both ends. i will be welding the back ends up with a piece and the front end will need some pie cuts before welding.

1

Simplest solution: put two 1x4s in the pipe. Then wedge subsequent 1x4s between the first 2. Wood slides past wood, but not past melty plastic.

0

I've deformmed pipe over a rectangular form for a very short length (a few inches). For a long pipe, I suggest making a box to go around the pipe. You may never get an internal form out after the pipe contracts while cooling.

127 Comments

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Do you think if u had a vase i was wraping the pipe around i could instead have a empty tube and use a heat gun to blow heated air into it vs using a stove. The heat gun was used for shrink wrap which im not sure if its going to be hot enough for bending the pvc pipe

1 reply

sorry, is it really necesary to use sand? isn't it possible with any other type of ground?

3 replies

Sawdust works. Dirt might work, if it stays loose and doesn't compact too much into a hard mass.

I think I would try that before the sand.
I have filled metal tubes with sand and did not like the results. The give of sawdust may work better even were it packed some in the tubes I bent.

Dry Dirt would probably work, I wouldn't use sawdust though as it could start on fire, making the possibilty of a PVC chemical fire more likely, which is bad for you and the environment. Anything powdery/dusty and Inert should work. (I.E. Doesn't Burn, and can take a lot of heat)

For a thing to burn, Chlorine is a more reactive oxidizer than oxygen.
I do not know what might be produced from PVC that may burn in absence of air. I don't even know any list of things that can be oxidizer.
I think I read that hydrogen and chlorine will just explode - or burn - to produce HCL in same manner that oxygen and hydrogen can be burned to produce H2O.
Just thought I'd throw that in .....

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?

3 replies

A sand tray in the oven? I know a race car driver who bent an entire acrylic windshield that way, but his girlfriend married him anyway!

The chemical decomposition of some chemicals creates oxygen, which helps to burn the resulting hydrocarbons. It's kind of like the experiment in science class were you burn wood to produce methane, capture it and then burn it also. This also makes burning wood more efficient. The problem is that the smoke produced tends to get in the way of external oxygen, which stops the flame from igniting and burning the methane. PVC is actually fire retardant though so I don't where the author got that from. Like the other commenter said, it is definitely possible because underwater fireworks burn with no additional oxygen.

the burning material provides its own oxygen. that's how things burn under water.

opeyumi: maybe you could use a can filled with sand? make the bend in your sand-filled pipe, cut off the ends with a tiny overlap; smooth them till they will just meet; empty the sand; gently warm your pipe on a flat bed of sand to get it in a single plane

How about using a hair dryer?

Please I need to make my pvc pipe a full circular bend and I don't know how to go about it any idea will be appreciated

1 reply

When jewellers make split rings, they bend a wire around a round dowel like a long spring and then cut through one side of the spring to make a lot of split rings.

You might be able to do the same with 1/2 inch pipe filled with sand and then wrapped around a larger piece of pipe. With luck, the split rings could then be forced, with heat if necessary, to have their ends together and held somehow. I'm just guessing. I have never done that. Good luck.

Thumbs Up. ( wish there is an icon here for thumbs up )

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!

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...!