Plastic plumbing pipe is nearly ideal for simple flutes. There’s no easier material to work with. Sanded clean and smooth, it’s attractive, requiring no finish. It’s waterproof, crack-proof, and nearly unbreakable. It’s fine acoustically, if you use the right dimensions. And once you develop a pattern, the pipe’s regularity allows a perfect flute every time.
The plastic we’re talking about is PVC (polyvinyl chloride), used for cold water supply, and its close cousin CPVC (chloro-polyvinyl chloride), for hot water. DO NOT use ABS pipe for flutes. Since it’s meant only for drainage, there are no restrictions on the toxicity of the chemicals added to it. Also avoid gray PVC electrical conduit, both because of possible toxicity and because of its greater wall thickness, which will hurt octave tuning.
Plastic pipe can be cut just like wood, though it dulls your tools more quickly. For drilling, use a very slow speed to minimize “grabbing” when the bit reaches the interior. Or avoid the grabbing entirely with “zero-rake” drill bits. You can order these specially or else modify regular twist drill bits by grinding. Find instructions for this in books on tools and sharpening. Don’t use flat bits—the size of the holes they make is not accurate.
After drilling, stick a long wood dowel into the tube to break loose the plastic “shavings” hanging inside. Smooth all hole edges and end edges with a narrow, very sharp knife blade or an apple peeler. If there’s too much hiss later when you play the flute, this may mean the mouthhole edge is too sharp.
Sand the tube at a sink, keeping the tube wet and using wet-and-dry sandpaper. This lets you rinse off your sandpaper as it clogs, and it also stops the dust from flying. (You don’t want this dust in your lungs. It never decomposes! If you “dry sand,” at least use a dust mask.) A heavy-duty scouring pad will also work, with some patience. Clean the inside with a bottle brush and water.
A good trick is to use a plumbing pipe end cap—a standard part—as a combination stopper and lip plate. Glue it on with plastic pipe cement, then drill the mouthhole through it. Apply the cement to the pipe surface only—not inside the cap—to avoid pushing the excess into the flute, where fumes can persist much longer. A flute made in this fashion should remain playable for thousands of years!
Use a different arrangement for pipe that is 1 inch or wider, so you can move the mouthhole farther from the end. At the top end of the pipe, place a slip coupling—a standard part used to join two lengths of pipe. Seal the opposite end of the coupling with a spigot plug. Again, always apply pipe cement so it’s pushed out of the joint, not in. Then drill the mouthhole through the slip coupling.
If you prefer a different way to stop the pipe, you can choose to do without a lip plate, but having one does improve the acoustics. One way to make one separately is to cut the pipe at your mouthhole mark and glue both pieces into a slip coupling. Or you can file the internal ridge out of a slip coupling and glue it over an intact length of pipe. If you don’t want the pipe completely surrounded by this coupling, you can first cut away some of its circumference.
A slip coupling can be used also as a tuning slide. After drilling your holes, cut away a tiny section of pipe between mouthhole and first fingerhole, then glue the coupling to one cut end. Be aware, though, that any arrangement with moving parts is likely to cause trouble as parts wear down.
Plumbing pipe flutes pick up dirt easily—an especial problem with white pipe. But you can easily clean them with a scouring pad, or with baking soda or bathroom cleanser on a damp sponge.
Mild fumes migrate out of plastic pipe for long after it leaves the factory, especially when heated by tools. If you make a lot of flutes over a long period, breathing these fumes could harm you—so work only with good ventilation. Pipe cement is much worse still, so you might want to use it outdoors. And don’t play a flute with a cemented part until the cement has completely dried. You can help this along by leaving the piece in direct sunlight or by a heating vent.
Following is the plan for a flute I designed in the summer of 1988. I call it the “Plumber’s Pipe.” It’s in the key of G and plays two full octaves. Of course, you might have to modify the design, depending on materials available to you. (For basic principles of designing and tuning flutes, see my book Simple Flutes.)
The flute is made from 3/4 inch CPVC pipe, plus a standard end cap. The actual exact dimensions of the pipe are 7/8 inch outside diameter, 11/16 inch inside diameter, 3/32 inch wall thickness. The tube length, with the end cap off, is 15-9/16 inches. The wall thickness of the end cap too is 3/32 inch, for a total mouthhole depth of 3/16 inch.
The chart shows the size of each hole and the distance from its center to the top of the flute tube—again, measured with the flute cap off. You can mark these distances on a piece of paper, a ruler, a dowel, or a length of pipe, then use this pattern to help place the holes on your pipe. Two holes are slightly offset as shown, for easier fingering.
There is no copyright or patent on this design. Feel free to make as many as you like, and to sell them too!