Polyvinyl chloride, or PVC, pipes have been around since the middle of the 20th century, but pipes aren't the only use for PVC. It can be fashioned into furniture, doors, siding and many other construction materials. A close cousin, uPVC, makes an even better construction material, and uPVC pipe has many advantages over PVC pipe.
The Difference Between PVC and uPVC
There is only one difference between PVC and uPVC and that is that PVC contains BPA and phthalates, which are two plasticizers that make it more flexible. The "u" in uPVC stands for "unplasticized," and because it doesn't have these extra materials, uPVC is often called rigid plastic.
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In much of the world except the United States, uPVC is used more widely for water pipes than PVC. The extra materials give uPVC superior resistance to chemical erosion, and its smooth inner walls allow water to flow more smoothly with less turbulence. uPVC is also resistant to a wider range of temperatures than PVC.
In the United States, PVC is the plastic of choice for sewer pipes and the transportation of nonpotable water. Neither PVC nor uPVC are suitable for residential water pipes, though. That function is fulfilled by CPVC, or chlorinated polyvinyl chloride.
PVC vs. CPVC for Plumbing Pipes
Like uPVC, CPVC is a close cousin of PVC. All three products are thermoplastics, but whereas uPVC is PVC that has been altered by the omission of plasticizers, CPVC has been altered by a free radical chlorination reaction that increases its chlorine content. This simple modification makes CPVC able to withstand higher temperatures.
PVC is rated for use at temperatures up to 140°F, whereas CPVC is rated for temperatures as high as 200°F. This makes CPVC more suitable for hot water systems than PVC, and it is the standard for residential water systems in general. Accordingly, you can buy CPVC pipes sized in accordance with copper tubing for addition to copper plumbing systems. PVC, on the other hand, is available only in nominal pipe size, which is the same as galvanized steel pipe.
When it comes to purchasing CPVC vs. PVC, you can distinguish the two by their colors. CPVC pipe and fittings are cream colored, while PVC pipe and fittings are white. The two materials require different cements and solvents and should not be used together.
uPVC is Rigid PVC
Because of its rigidity, uPVC is a better construction material than PVC. When you purchase PVC decking boards, railings or siding material, you're buying products made from uPVC, not PVC. Some sewer systems in the United States are made from uPVC pipe, but few water systems are made from it.
The chemicals that make PVC more flexible and are accordingly left out of uPVC are BPA (Biphenol A) and phthalates. Neither of these is highly toxic, but neither is completely nontoxic either. BPA is toxic only at very high concentrations, while certain types of phthalates, such as Di (2-ethylhexyl) phthalate, are an endocrine inhibitor and may cause cancer. Despite this, many consumer products, including children's toys, are made with phthalates.
The toxicity of plasticizing materials may be low, but it is one reason why PVC pipes are undesirable for transporting residential water for drinking. If you find them used around the home, they are outside transporting water used for gardening and landscaping. When you see small plastic pipes and components in doctor or dental offices, they are usually made from uPVC, not PVC, and the presence of the mildly toxic plasticizers in PVC is the reason.