PVC (polyvinyl chloride) is one of the most used materials in plumbing, irrigation, electrical cables insulation as well as construction. It is cheap to produce, easy to install and can last just as long as other materials.
PVC is also a very versatile material and that is where there are several types of PVC pipes in the market, each with different properties. Two of those types are UPVC and CPVC.
The main difference between UPVC and CPVC is that UPVC is unplasticized while CPVC contains plasticizers and is also chlorinated. As a result, UPVC is quite rigid while CPVC is flexible and can withstand high temperatures.
As a matter of fact, the “U” in UPVC stands for unplasticized while the “C” in CPVC stands for chlorinated.
UPVC pipes are not approved for the supply of drinking water. Pipe manufacturers use lead as a stabilizers which is toxic and can leach into the water.
CPVC pipes are safe and certified to supply drinking water. No harmful toxins in CPVC can leach into the water and contaminate it. CPVC pipes’ high temperature rating also means that they can be used to supply both cold and hot water.
UPVC pipes can only handle temperatures of 1400 F before softening. On the other handle, CPVC pipes can withstand temperatures as high as 2000 F.
UPVC pipes are not suitable for the supply of hot water. The maximum temperature UPVC pipes can withstand before starting to soften is 1400 F, which is the temperature setting for most water heaters. CPVC pipes are more suitable as they can handle temperatures of 2000 F.
UPVC (especially schedule 80 pipe) is stronger than CPVC and PVC and that is why it is also known as rigid PVC. As a result, UPVC can be used instead of wood in construction and as a substitute for cast-iron in heavy-duty plumbing.
UPVC vs CPVC
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Let us now look at the properties and characteristics of both UPVC and CPVC in more details.
1. Chemical Composition
UPVC simply means unplasticized polyvinyl chloride while CPVC stands for chlorinated polyvinyl chloride. CPVC has therefore undergone a chlorination process and also contains plasticizers (BPA and phthalates).
CPVC is produced by the chlorination of a PVC polymer through a free radical chlorination. The reaction is started by UV energy which decomposes chlorine gas into radicals.
In the reaction, the chlorine radicals react with PVC whereby hydrogen atoms are replaced by chlorine atoms. Usually, the chlorine content in PVC is usually around 57% but after chlorination it increases to around 69%.
2. Flexibility
Naturally, PVC is quite a rigid material. That makes it undesirable for certain applications like when you want to bend it or snake it through a curve.
That is the main reason plasticizers are added to PVC material. Plasticized PVC like CPVC pipes are quite flexible and can therefore be bent. On the other hand, UPVC is rigid and cannot be bent, lest it cracks.
Due to its strength and resistance to bending, UPVC is widely used as an alternative for wood in construction especially in the manufacture of window and door frames.
UPVC door and window frames can be made to look exactly like wood and do not change shape despite the weather conditions, although at very high temperatures they can be deformed/reshaped.
CPVC pipes are a great choice for residential plumbing especially where flexibility is needed. Drain lines don’t always follow a straight line and sometimes may need to be installed around a curve and that is where CPVC’s flexibility comes in.
3. Temperature Limits
The main reason CPVC goes through the chlorination process is to increase its ability to handle high temperatures. CPVC pipes are the only plastic pipes allowed to be used in the supply of hot water.
As I mentioned earlier, UPVC will only handle temperature of up to 1400 F before it starts to soften. Thanks to the chlorination process, CPVC can withstand temperature of up to 2000 F.
In most homes, most folks set their water heater thermostats at between 120 and 140 degrees Fahrenheit. Using a pipe with the exact temperature limit as that of the water is unsafe and that is why UPVC pipes are not allowed for use in hot water transportation.
Although unrelated to temperature, another thing that makes CPVC pipes better for use in supply of water is that they are available in both nominal pipe size and copper tube size.
You can therefore replace a copper water supply system using CPVC. You just need to specify which connection you need when buying the pipes.
4. Water Safety
When it comes to safety, especially of drinking water, plastic pipes are less preferred by some folks over other materials like copper. The question that most people would want answered is whether these pipes are actually safe for supply of potable/drinking water.
Plasticized PVC pipes are banned in some countries due to the plasticizers added especially BPA. CPVC pipes (plasticized) are however legal in the United States and are actually certified for supply of drinking water.
BPA (Bisphenol A) is also used in food and drink packaging and containers. According to United States Food and Drug Administration (FDA), the current BPA levels in the packaging, (same as those used in CPVC) are safe.
Despite the lack of plasticizers, UPVC is not certified to be used for drinking water. The manufacture of UPVC pipes is not controlled and hence overload of filler materials is not uncommon.
Apart from that, lead is used as a stabilizer by some UPVC pipe manufactures. Lead is one of the most toxic metals and will leach into the water and is especially harmful to pregnant women and young kids.
CPVC pipes however are certified for supply of drinking water since they only contain tin stabilizers, which is not harmful. The BPA levels are also quite low and are therefore considered safe.
5. Corrosion Resistance
Unlike cast-iron and other type of metal pipes, both UPVC and CPVC are corrosion-resistant and will therefore not corrode.
One advantage of CPVC is that it will not be affected by chlorine present in the water. The high chlorine content also prevents the growth of bacteria inside pipes, which is not the case with UPVC.
UPVC pipes however have a very low friction coefficient. The inside of UPVC pipes is way smoother compared to CPVC pipes meaning fluids flow through them with limited resistance. This also prevents the growth of sludge/scales inside the pipes.
6. Pressure Rating
Unknown to most people, the pressure rating of a pipe reduces with increase in temperature. At 730F, both UPVC and CPVC have the same pressure rating. However, as the temperature increases, CPVC pipes maintain their pressure rating better than UPVC pipes.
For example, at 1300F, UPVC will have a de-rating factor of 0.31 compared to CPVC’s 0.57. According to this PVC pipes pressure chart, a 10-inch schedule 80 pipe has a pressure rating of 230 psi at the normal temperatures.
When the temperature is raised to 1300F, UPVC allowable pressure limit will be (0.31 x 230 = 71.3 psi) while that of CPVC will be (230 x 0.57 = 131.1 psi).
Conclusion
UPVC is basically unplasticized PVC which is used to manufacture rigid pipes for heavy-duty plumbing and also to make door and window frames. On the other hand, CPVC is both chlorinated and plasticized PVC that is used to make flexible pipes for drainage, irrigation as well as supply of cold and hot water.