Re: Bending PVC
Posted by DICK on August 10, 19100 at 09:38:04:
In response to Re: Bending PVC
: How can I bend 2" PVC pipe using a heat gun? Only a slight curved bend is needed, less than 40 degrees.

PVC is a thermoplastic, which means it is heated and molded to shape without any chemical changes. typical molding temperatures for PVC are 300 to 400 deg F. You should be able to heat it to about those temps without fear of weakening the base material. Actualy it will become fairly soft at well below that temp. Molding is usualy done at pressures of 1000 psi++.

This doesn't mean that it is easy to bend it. Well actualy it is easy to bend it, but it can be hard to maintain flow area and structural integrity. first problem is it will tend to flatten and kink, try bending your garden hose it will behave similar. you can only go to a certain radius before it starts to flatten and reduce flow area. this can be counteracted by putting a long spring in the id (may be tough to get back out) or filling the id with sand.
Second problem is thinning of the wall on the outer side. This would not be so much of a problem if it was uniform, but it never is. minor variations in heating and material will garuntee that you will have thin spots.
The seriousness of these problems depends on the radius of your bend. the total angle doesn't matter.

If you are getting the idea that this is not a simple process, you're right. The sensible thing to do is to buy fittings and glue them up.

If you are not sensible, build a wooden radius form to bend the pipe around. cut a piece of PVC about 3' longer than the distance around the bend. cap one end, pack it full with sand, shake it down good so it is solid. cap the other end. drill a 1/16 hole in each cap and then cover it with tape. fasten one end to the radius form. start heating near this end. heat about a foot or so of pipe at a time until it will bend around the form with just light finger pressure. Move down and heat another section.

You may have to repeat this with several pipe sections until you get the techniqe down.

You will end up with a $50 -$75 pipe fitting that only took 2 days to make.

Depending on where this piece is to be used, consider pressure testing to double actual working pressure. Bending will reduce the burst pressure of the pipe, but it is impossible to estimate how much.

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