What is the difference between PVC and CPVC pipes?
Plastic is a wonderful material that has revolutionized almost every aspect of modern life. The plumbing industry is no exception. Since the introduction of plastic pipes in Germany during the late 1930s plastics have continued to develop and there are now several excellent options for plastic piping, each with their own advantages and disadvantages. PVC is of the most widely used plumbing materials around the world for fresh water supply, drainage and irrigation applications. Rigid PVC piping comes in two main forms: PVC and CPVC. This article will describe the primary differences of the two kinds of materials.
First we need to understand what PVC and CPVC are. PVC stands for Polyvinyl chloride, the third most produced plastic in the world, after Polyethylene and Polypropylene. PVC is a white brittle powder until mixed with plasticisers and other additives which give it its most desirable properties. CPVC is PVC resin that has been chlorinated (Chlorinated PVC). Adding extra chlorine to the PVC resin increases several of its most desirable properties.
1. Temperature resistance
Temperature resistance is the major useful difference between PVC and CPVC. PVC, like any plastic, begins to soften and loose its strength and rigidity as temperature increases. This means a reduction of the maximum pressure a PVC pipe can withstand as temperature increases.
For example: at 73°F (22.8°C) 2” Schedule 80 PVC pipe is rated for up to 400psi (2.76Mpa). However if the temperature of the environment or fluid rises to 110°F (43.4°C) the same pipe can only withstand 204psi (1.4Mpa) – a reduction of nearly 50%. This problem increases quickly as temperature rises, so much so that PVC is only rated for use up to 140°F (60°C). CPVC can withstand significantly higher temperature before losing strength: a 2” Schedule 80 CPVC pipe can withstand 288psi (1.99Mpa) at 110°F (43.4°C) – a 41% increase in maximum pressure! CPVC has a max temperature rating of 200°F (93.3°C) making it the material of choice for high temperature applications.
2. Chemical Resistance
PVC and CPVC are resistance to a wide range of aggressive chemicals found in many industries. That is why PVC piping is so desirable compared to other piping materials such as steel or copper in many applications. Both PVC and CPVC are resistant to many strong and weak acids, weak bases and salts. Where PVC is resistant to these chemicals, CPVC can carry that same resistance at higher temperatures.
However there are some notable differences between the resistances of PVC and CPVC. PVC is more resistant to ammonia and other chemicals containing high amounts of chlorine. In demanding applications it is best to check with your supplier to confirm which material would be best for your application. You can check out the resistances of several common piping materials, including PVC and CPVC against hundreds of chemicals here.
PVC is a very economical piping material compared to the other piping materials such as copper and steel. Due to the more complex manufacturing process and lower demand CPVC can be significantly more expensive than PVC, up to 6 times more expensive. Solvent welding PVC and CPVC pipes and fittings also require different types of primers and cements with CPVC cements being more costly than PVC cements.
Both PVC and CPVC are excellent piping materials for many applications but where temperature is a concern it is best to use CPVC rather than PVC. Both PVC and CPVC have a wide range of chemical resistances you should check which is best for your specific application. Due to the cost difference between PVC and CPVC, PVC is the best choice for general applications and CPVC should only be used when necessary to save cost. Now that you understand the differences between PVC and CPVC piping you can make the best decision for your project. To see a huge selection of both PVC and CPVC fittings and valves at the best prices check out www.Petrampvc.ca