Bending PVC pipe - Just because you can

Have you ever found yourself putting in that new sprinkler system for your garden and right in the middle of the project discovered that you are out of 45 degree fittings?  With this simple technique, you can heat bend custom fittings in any kind of PVC pipe.

The secret to the process is using a controlled heat source and spreading it out. In a word keep: it moving, keep it rotating. (OK, that was more than "a" word)

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Step 1: Heating the pipe

PVC pipe is created by a process called extrusion.Extruded products are all around you: Spagetti, macaroni, aluminum door thresholds, vinyl window frames, plastic bags ... even plastic water bottles (which start as extrusions before they are blow molded) ... all these are extruded.  In the case of PVC pipe, chips (or beads) of rigid PVC plastic are heated up to a molten state and forced through a hole correspondng to the shape desired - in this case, a pipe.  As the pipe is extruded, it is held in a straight line until it cools into a solid length of pipe. 

PVC is a thermoplastic - which means that it becomes soft when heat is applied.  You can use this little tidbit of knowledge to heat and re-form the pipe to a new shape without compromising its physical properties ... if you are patient.

The best tool for heating the pipe is a heat gun - available for around $25 from your local hardware big box or online (search: 1500 watt dual temperature heat gun).  You can also take your piece of pipe into the kitchen and use your stove top - just make sure your wife isn't home.  What doesn't work so well is a propane (or MAPP) torch as the heat is too concentrated and charring the PVC is highly likely. Save the torch for making your PVC diggerydoo ... but that's another instructible.

The key to the technique is constant movement - move the PVC pipe or the heat source back and forth over a 12" or so area and keep the pipe rotating all the while.  After 3 or 4 minutes, the piece of pipe will start to sag.  Keep it moving and rotating and begin bending it while rotating it - all the while keeping the heat on. 

Comments

[FlexPVC]

This is not exactly true. The only way to release the chlorine gas from the pipe is to heat it to break the Chlorine-Carbon bonds, ie combustion. Which a heat gun will almost never do. However, doing it over an open flame it is possible, especially when using a torch. If you see the pvc turning brown from the heat, then yes, it's possible on a micro level, some Chlorine gas would be released. If it turns dark brown, or black, you have definitely released chlorine gas. Probably about as much as you do when you jump into a swimming pool. My "datasheet" is my college diploma in Chemical Engineering. But you are not convinced by that, pvc.org has a tremendous amount of information on pvc.


For bending small pipe in non-complicated bends a Morris PVC Pipe Spring Bender
can be used.They make then for up to 2.5" pipe, but anything over 1" requires some mechanical advantage. ie, a very long piece of pipe that you are bending in the middle, and 3 people. One in the middle, and one on each end of the pipe.You can only make single simple bends with the Spring Bender.


We use a special oven to make hoops and u-bends. It requires experience to get it correct. Temperature and technique are critical to get pieces you can use w/to being deformed.

[AppleDad]

Holy smoke, guys! Why are so many of you worrying so much about the chlorine exposure?

First, it's almost certainly in the water you drink, so using it in a potable system should be fine.

Sure, chlorine gas is toxic, but unless you are performing this practice indoors, 8 hours a day, 5 days a week, your exposure to the low levels you might receive will do little more than give you a sore throat. You'll breathe higher levels of chlorine gas at a public swimming pool.

If you're a weekend DIY warrior, and you're working outside with or without a breeze, you'd be hard pressed to exceed exposure limits.

And, yes, there is documentation about this.

[pcooper2]

I've bent 1-inch PVC pipe for a backyard irrigation project using a Coleman® Powermate® 15,000 BTU propane radiant heater mounted on a 25-lb propane cylinder. It provides even, flameless heat over a larger area than an electric heat gun can and allows one to make gentle, large-radius bends that minimize turbulence and dynamic pressure drop. Since the heater is securely mounted, it also makes it easy to turn and move the pipe with both hands in front of the heater, then bend it without delay as soon as it is soft enough to work. On occasion, I've also used same-size gray PVC electrical conduit bends in place of PVC elbows, since their large radius reduces pressure drops. They're not explicitly rated for water use, but I reason since Schedule 40 PVC is Schedule 40 PVC, it should work fine, regardless of color. Jobs I did over 10 years ago are still working perfectly.

[wisegye]

Wow ... lots of talk about bad vapors from heating PCV. The truth appears to be "don't heat it to the point of charring or degradation" ... because if you do, it can produce dangerous gases.

Here's a link to an MSDS for PVC. A search for MSDS PVC ought to net more results.
http://www.solusii.com/PDFs/PVC-MSDS.pdf

If you take the time to read it you will find that it says "Resperatory Protection" is "Not normally required. If overheating results in decomposition resulting in smoke or fumes, a NIOSH/MSHA approved combination high efficiency particulate filter with organic vapor cartridge can be used ... "

If you are worried about the fumes, don't heat your PCV ... or get yourself one of those approved resiprators. This ain't rocket science ... just do your own homework.

[jovino]

Beware that when heated, PVC will off-gas a colorless, odorless fume which is TOXIC.

Do your homework, kids.

[pcooper2]

It will only do that if heated to the point of charring or ignition. If it's heated just enough to soften it for bending — the objective in this Instructable — it's safe. I've done it many, many times indoors and outdoors with no ill effects whatsoever.

[jovino]

Do you have a datasheet supporting your findings?

[pcooper2]

Datasheet? I'm obviously alive and well as I write this comment.

[heathbar64]

I've heard of filling the pipe with dry sand to keep it from kinking. I've also seen where you can heat and bell out the end of the pipe so you don't need a coupler.

[dadokon6]

Hey!
I remember years ago I saw an article about a man that was using pvc pipe to make "futuristic" lamps (it was an ooooold article). Anyway, what he did was take 1" to 1-1/2" pvc pipe, cut it to longer than he thought he would need, and push a cap (not glued) on the end. Then he would heat up a disposable casserole dish full of sand in his oven (don't remember the temp-sorry) and then would pour the sand into the pipe. As I recall, after a few minutes the pipe would soften and then he could bend it without it kinking, When it was in the shape he wanted he would run cold water over the pipe and into the sand to cool everything off and stiffen it up again. The rest was just regular lamp building stuff. But I always thought this would be a handy thing to try someday!! I've used a heat gun to soften pvc to make holsters for various tools myself. Just don't char it because it does release chlorine gas which is really nasty stuff. Kill you quick. Your mileage may vary.

[The Ideanator]

Standard pipe bending procedure.

[Blenderizer]

My scout troop used the hot sand method to do snoeshoes a while back. The process was essentially to cook the sand until it was fairly hot, then pour it all into a cut-to-length PVC pipe. Then two people with gloves would bend the frame into a wooden jig, and hit it with a heat gun if needed. They actually came out really well. I have about 25 sets of snowshoe frames (unfinished) hanging in the garage... 0_o

The end effect looks like this: http://i.ytimg.com/vi/3RSIzMTfX7A/0.jpg
(bindings are made of rubber tire innertubes from old tractor tires with some bolts for traction. I'm sure theres an instructable out there for doing them if you looked)

[Kozz]

That sounds like a fantastic idea. Is that photo from a tutorial or instructable somewhere? I'd love to read about it, especially the construction of the jig and the bindings.

[General Lee Stupid]

My troop did the same thing. We made a couple and they turned out great. I was really impressed with how well the snowshoes ended up. Definitely one of my favorite projects we did

[wisegye]

Cold bending PVC can work - especially in smaller sizes - 1/2" is easy. I challenge anyone to try to cold bend anything larger than 1". And ... if the pipe has become brittle with age, it's going to snap regardless of how small it is.

I had an exterior electrical J-box made-up with 6 PVC conduits w/ wires run and everything that got rejected in an inspection ... supposedly because there was a stand-pipe too close in front of it. I put a canvas tarp over the whole thing (to help contain the heat) and got out my heat gun. It took about 15 minutes to heat up all 6 conduits but once everything was nice and hot, I was able to rotate the entire J-box a full 90 degees, conduits still in place. Another 5 minutes to cool it off and it looked perfect (and got passed in the next inspection).

[jimvandamme]

I've bent 3 inch drain pipe by holding it over the kitchen stove and rotating it until got rubbery. Then I put about a 3 degree bend in it to make it drain well. You're not going to make pretzels out of 3 inch DWV pipe.

[macrumpton]

FYI you can bend pvc without heat using a long spring like you use for screen doors. You need a spring that is a little smaller than the i.d. of the pvc, and you tie a string to one end of the spring so you can get it out of the tubing after your bend. Make sure the spring is centered on the area you want to bend and just bend the pvc over a shape with a somewhat tighter curve than you want to end up with, and then pull the string and spring out.

I could not believe that this actually works but it does and it is fast and easy.
BTW there are lots of youtube videos of that.

[dropkick]

I'd be wary of doing this with cold PVC.
I had done the pipework the day before for a bathroom vanity with CPVC which is less brittle than PVC. I hadn't put in the vanity yet as I was working on the toilet beside it. My Dad came into the bathroom and bumped the pipe. It snapped off cleaner than a whistle.

[pcooper2]

CPVC is MORE brittle than PVC. It's also getting harder and harder to find, since it is being replaced by PEX in most applications for both hot and cold water. I wouldn't use CPVC for new construction, only for repairs on existing installations.

[dropkick]

I don't know. Maybe it is.
But when I had experience with both (over 30 years ago) it sure seemed like PVC was the more brittle of the two.

[drstock]

Or even better: buy/borrow a spring bender. They cost about 30-40 dollars, but if you know an electrician he is bound to have one or two.

[databoy]

PVC pipe is toxic. Never use PVC pipe or conduit for drinking water. The chemicals used to manufacture PVC pipe leach into the water and may cause stomach and liver damage.

Heat bending PVC pipe or conduit is useful only in an absolute emergency.

Bending conduit using a naked gas flame or an electric heat gun is not as easy as presented and the PVC pipe or conduit emits very toxic carcinogenic gases when heated.

Electrical PVC conduit is a very quirky material to heat bend. Even with perfect attention and skill, even new PVC pipe and conduit will not dissipate heat evenly, and will loose heat very fast when the heat source is moved. Old or PVC pipe and conduit exposed to the sun’s UV rays is too brittle to heat or spring bend; it will snap.

New PVC pipe and conduit is designed to be cold bent with an internal spring bender. As an apprentice electrician I spent 4 years on high rise buildings bending ¾ inch conduct, laying it on steel before the concrete floor was poured.

I have seen electricians bend ¾ inch new PVC conduct over their knee cap making a perfect bend, without the use of heat or a spring bender.

That was over 40 years ago. The modern range of PVC conduit almost bends itself.

In fact, most Australian electricians don’t use PVC bends any more. They use flexible corrugated PVC conduit and couplings.

[pcooper2]

PVC produces toxic fumes only when it is burned, not when it is merely heated to soften it. PVC pipe is code-approved in most places on Earth for potable cold water and is considered safe, as is PEX tubing.

[jsolterbeck]

Err . . . maybe I didn't read closely enough, but are we forgetting http://www.pvcbendit.com/ ? One of many heat-based PVC bending products.

[bo88y]

They start at $219.00

[Tim Temple]

On shipboard we had a couple of plastic water lines that live steam backed up into. they were drooping like cooked spaghetti from the stanchions!

[jack8559]

I work at a place that makes pvc conduit, and the way we make bends is to insert a rubber hose after rotating the pipe under a heater, pressurize the hose so it won't collapse and bend the pipe and clamp it down to a jig. After that, we submerse the pipe (and jig) with the hose inside it into water to re-harden it so it will retain its shape. After a few minutes, remove the jig from the water, take the pipe off, let the prssure off the hose and remove it and you're done.

Standard pvc pipe can also be heated in oil until it reaches around 375 dgrees F and insert a larger diameter pipe, rod, or other tool to make the bell end for a pipe then cool with water so it will retain the shape. I did this where I used to work because all the hardware stores were closed and we had a pipe that HAD to be repaired and we had no couplings....