i am wondering how to do perfectly curved pipes that maintain the same diameter/radius throughout the whole thing. How?
Heres what to do:
Add a bezier curve. (this will be the shape of the pipe)
Add a bezier circle. Name it ‘circle’ (this will be the thickness of the pipe)
Select the bezier curve, press F9, where it says ‘BevOb:’ type: ‘circle’.
You should now have a pipe.
Hope this helps. 
Awesome, thanks a ton! Was just wondering how to do that myself for some greebles.
Great way of making ropes and hoses as well. There’s no way any normal human would be able to do this using subsurfs.
great! thanks! thats just what i wanted. now i can do some detailing!!! 
There were quite a few threads about that already and I can only tell you not to forget about the Curve Deform tool, too. Using that you can achieve quite complex pipe structures (and not only that) very easily.
It may involve a little more setup to work properly but it is worth it, at least in my opinion.
Has the twisting been fixed in 2.37? Last time I did this in 2.36 and no matter what I did (short of keeping it in one plane), I would get a twist in tube.
No.
%<
Is there any hope for a fix?
I reread the manual a little last night since I clearly needed to and I wanted to add one other method for making curved pipes. Use the “lathe” or spin tool. It can be alot more precise for a pure 90 degree bend as long as you place your 3D cursor correctly.
Just add a tube mesh, select the verts on one end, place the cursor and set the angle and steps in mesh tools panel (F9) and press the spin button.
It will spin using the view so it can be very useful when combined with the * key to make pipes along side a hull without having to manually align them.
that’s weird, i thought i just replied to this thread, but now i don’t see my post. i must have hit the preview button by mistake or something. i was going to say the spin tool on a circle, however. and, of course, you can also obtain other degrees by deleting rows of vertices. another slightly more tedious way is to simply set rotation for ‘around 3D cursor’ and use extrusions.