Manufactured using a combination of plastic and vinyl, polyvinyl chloride (PVC) pipe has been used for decades to carry water, wiring, and sewer lines. Though controversy has caused some to question the safety of PVC pipe, the PVC Pipe Association insists that this kind of piping has proven a clean, safe, and effective option. When heated, however, PVC pipe can lose its usefulness and can produce dangerous fumes, though it is less flammable than many other building materials.
On a practical level, heating PVC pipe can cause distortion. With a melting point of about 176 degrees Fahrenheit, PVC pipes may bend as the material approaches this temperature. This causes some concerns not only for the usefulness of the pipe but also because the pipe's materials might leech into tanks or water lines when the PVC pipe is exposed to temperatures near its melting point. Active PVC pipes should never be heated beyond 158 degrees.
Another potential concern about heating PVC pipe is that the material might catch fire. In relation to other building materials, PVC pipe actually isn't that flammable. In fact, it requires temperatures of about 840 degrees Fahrenheit in order to ignite, whereas wood requires temperatures of only about 500 degrees. Still, industrial fires and even house fires can sometimes produce temperatures hot enough to make PVC pipe catch fire.
Smoke and Vapors
Perhaps the most serious concern when it comes to PVC pipe is the toxins released when PVC burns and produces smoke. If PVC pipe does become hot enough to catch fire, it releases dioxins into the air, which are harmful to both humans and the environment. Additionally, once PVC does catch fire, it will produce more smoke than many other building materials. Even when PVC is just heated, it also may release carcinogenic vapors that can cause cancer. The best way to avoid these dangerous fumes is to prevent PVC pipe from burning or to wear a gas mask when forced to heat PVC pipe.
PVC pipe releases heat at a relatively low rate. Thus, if PVC does catch fire, it is less likely to ignite nearby materials than many other organic building materials. This may be beneficial in construction and may slow fires that do break out in areas with PVC pipe.