The problem with heating the pipe is that there is a fine line in temperatures between the point at which PVC pipe is flexible to form bends and the melting point of PVC. PVC melts at about 176 F. The fine line is that somewhere around 170 F is the temperature for making long radius bends in pipe.
Like all materials, PVC expands as the temperature rises and contracts as the temperature falls. Because the length-to-diameter ratio of PVC pipe and tubing products is generally very large, the change in length due to temperature changes is most noticeable.
You can bend PVC pipe by applying heat to the part where you want the bend. PVC is what scientists call an amorphous polymer, meaning the particles that make up its structure are not arranged in any fixed arrays. Therefore, applying heat to the PVC will soften it and make it easier to bend.
PVC is thermoplastic, which means that it softens when heated and can be formed into all sorts of shapes. You can stretch and compress it and it will keep its shape when chilled.
Like most materials, PVC and CPVC become more brittle at low temperatures, especially at temperatures below freezing (32°F).
At what temperature does PVC soften? Softening begins at around 200 degrees F. Material becomes viscous at 350 degrees F. Material will char at 425 degrees F.
PVC laid above ground and exposed to sunlight may degrade faster than normal. The sun’s ultraviolet rays can break down the structure of PVC material, making it brittle and fragile.
Will boiling water damage PVC pipes? As a general rule of thumb, hot, boiling water can soften or even slightly melt the joints in your PVC pipes, so YES, if you regularly expose this type of pipe to hot water – it can damage it, cause leaks and eventually need to be replaced.
While PVC is excellent for water supply lines and DWV applications, it is not recommended for hot water distribution systems as it can only withstand temperatures up to 140℉. However, CPVC and PEX can withstand temperatures up to 200℉. Most water heaters are set to heat water to no more than 140℉.
Temperatures from 99 to 135 degrees Celsius are ideal for bending these hoses. For PVC bending this is not a problem. Once the Bending is connected to a power source, it can take up to 30 minutes for the hose to heat up. We were able to achieve sweeping 90 degree bends with tubing this size.
Maximum operating temperature for PVC is 140°F. Exceeding the maximum operating temperature may result in system failure and/or property damage.
It can be made softer and more flexible by adding plasticizers, the most commonly used of which are phthalates.
PVC is a thermoplastic – which means it softens when heated. With this little nugget of knowledge, you can heat the tube and reshape it into a new shape without affecting its physical properties…if you’re patient.
If you just need to melt the PVC enough to make it pliable, a heat gun will do the job. If you need to melt the PVC enough to mold and shape, you’ll need a double boiler.
High Water Pressure
Water pressure in excess of 80psi can cause PVC pipe to expand and rupture, significantly reducing its expected useful life.
The plastic softens and loses its stiffness as the material temperature increases and if you heat it long enough or exceed the limit of its operating temperature range, it will begin to deform.