PVC is the plastic pipe used in most new homes for cold and hot water. It has almost completely replaced copper. At one time misguided environmentalists were very much against the use of PVC because it supposedly created unwanted emissions when it was being produced and was not considered bio-degradable. Actually, when compared to the pollution caused by copper mining, processing of copper ore, and production of copper pipe, the use of PVC is a great boon to us all - unless we would like to do without plumbing entirely. PVC does degrade - especially when exposed to sunlight - but this process does take a long time.
PVC is made in batches. Each batch varies slightly in its dimensions and flutemakers who use it should also use a micrometer to measure it if they wish to design a correctly tuned flute. PVC comes in various sizes. If one wishes to make a flute that is tuned to middle C, C# or D above middle C, 3/4 inch schedule 40 PVC is ideal. If one wishes to make a flute that is tuned to G, G#, or A above middle C, 5/8 inch schedule 40 is ideal. CPVC (hot water pipe) in the 3/4 inch size is ideal for an easily played flute in the keys of F, F#, or G. Both the 3/4 inch and the 5/8 inch sizes of CPVC are great for making what I call the Native American slot flute (See Creating and Using Grandfather's Flute by this author).
PVC schedule 40 is white or cream-colored and has a wall thickness of about 1/8 inch. CPVC is tan or light brown in color and has a much thinner wall. Schedule 125 PVC is white with a very thin wall and is also very good to use for slot flutes but is less durable than CPVC. All PVC comes in a "slick" form with lettering on it that requires removal. The use of waterproof emery paper on the flute under water us the best way, in my opinion, to remove the lettering and put a proper finish on the flute. Oil stains can also be used to create a finish that looks like wood if one does not like the natural color of the PVC.
Schedule 80 PVC is gray-colored with a very thick wall. It is usually used for holding electrical wiring but may be used for flutemaking. It is usually softer than other types of PVC which makes it more easily carved by a knife in the later stages of making the flute, but is not very good for making transverse flutes (fife or bansuri type flutes) because of the thicker wall.
PVC flutes sound fine. Most of the sound that a flute makes is from the shape of the flute rather than the material of which it is made. PVC is more perfectly dimensioned than a wooden flute made with a router or a boring tool. Because PVC is accurately dimensioned to a thousandth of an inch, it is perfect for making flutes designed with my computer Flute Design Program which is also accurate to a thousandth of an inch. In tests where one was blindfolded before listening to a PVC flute versus a wooden flute, the listener could not tell which flute sounded best and often picked the PVC flute over the wooden flute. However, most people are prejudiced in favor of the wooden flute due to its appearance.
Unless subjected to extreme heat such as leaving the flute under the windshield of a car that is parked in the sun (yes, this has happened), a PVC flute is much more durable than any wooden flute. Such flutes are ideal for backpackers and hikers and can even be used for self-defense just as the ancient shakuhachi of Japan was used. There was a time when I was younger that I was riding a bicycle down a hill. My favorite PVC transverse flute was dangling with a cord from the handlebars. Of course, the flute was eventually caught in the spokes of the front wheel. The rear of the bicycle moved upward abruptly in the rear and came down on top of me. Although I landed on the end where my head (the thickest part of me) was, I survived. Several spokes in the front wheel of the bicycle had to be replaced. The flute was scratched a little bit but was easily restored to its prior condition. I still have it and it is still my favorite transverse flute.