Introduction: Bend PVC Pipe
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.
AndrewKFletcher made it!
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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
Much easier to buy the square PVC drain pipe that is available than to try to make it.
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.
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.
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.