While commercial vaporizers use it, I don't believe that PVC is safe enough for this purpose. Don't use it. As you can see I I've read about leeching in medical products (while they were using specific chemicals), and also read that the PVC should not be heated over 180F which is not enough. Silicone tubing can be bought online. I use thin copper tubing.
Where I live smoking tobacco is restricted to people 18 and over. If your under 18 don't make this, don't smoke, or vaporize, or whatever. While vaporization may reduce the health hazards associated with inhaling plant material, I'm certain that it does not completely eliminate them. Don't smoke. It's addictive and bad for your health. Depending on what region or country you live in, it may be illegal to consume specific herbs. Make sure that the herbal blend you choose is legal in your region. This guide is not intended to assist in the illegal (And highly immoral) consumption of banned plant materials.
This vaporizer is a fire hazard. It's cheap and easy to make, but there's a trade off. This one cost me about $25. A similar commercial vaporizer would cost 150-250$.
You might consider buying one of those wall timers so that if you leave your vaporizer plugged in by accident it will only run as long as you set the timer for. This is a must if you plan on vaporizing any herbs which may induce forgetfulness. Don't start a fire!
Further I've been warned that copper fumes are vary dangerous. I don't think copper will fume at the temperatures I'm subjecting it to.
That said the consensus among many smokers is that the most sure healthiest thing to smoke out of is glass. If you find a good way to do this with glass, more power to you! For now my brass on glass design might be the best DIYers can hope for.
One more warning: Don't use a soldering iron that has come anywhere near solder. Solder is super poisonous nasty stuff. Just buy a new one. They are really not that expensive.
Step 1: Materials.
This is for the socket where you plug your vaporizer into. With the timer you set the timer for as long as you plan on using your vaporizer so that it shuts off automatically. If your at all forgetful this is a must. Some herbs have even been suggested to bring about forgetfulness. If you plan on vaporizing any such herbs the timer is must!
A (few) bottle(s).
I used a large 1.75 liter Gvori vodka bottle.Gvori is my favorite vodka, and their bottle is awesome. Other bottles should work, but you'll want to vary the end of the fitting that goes against the bottle (more on that later). This should be free. If you don't have a good bottle laying around someone near your probably does. Since breaking a bottle is a chaotic thing you will want to have back-up in the case your first doesn't work (it probably won't).
A soldering iron (at least 40 watts).
I used a generic radio shack one. It cost about 7$. A radio shack one is probably best since their design is so simple. Anything more complicated will only get in your way.
Thin copper tubing.
I used 1/4 inch. It's flexible, but don't bend it into too sharp of an angle or you will get a kink (they're almost impossible to get out).
A brass or copper fitting.
I used a copper fitting I picked out which allowed the copper tubing to barely slide through it on the narrow threaded end, that was big enough on the other end to make a good bowl and fit against the neck of the bottle. The one I bought from lowes is labled 3/8" flare X 3/8" FIP. I would suggest looking ahead in the instructions before you purchase any type of fitting for this project.
Two pairs of pliers, at least one of which is needle nose
A serrated knife or dremel for cutting through the plastic handle of the soldering iron.
A coat hanger.
The type bought at smoke-shops to go in the bottom of a pipe.