PVC pipes are the most preferred pipes by plumbers especially when it comes to the installation of drain lines. They are inexpensive, lightweight, corrosion-resistant and are not affected by tree roots unlike cast-iron pipes.
Here are the 6 types of PVC pipes:
- Unplasticized PVC (PVC-U) Pipes: PVC-U pipes are rigid, durable, and commonly used for potable water distribution, wastewater systems, and industrial applications. They are known for their resistance to corrosion and chemicals, making them suitable for a wide range of uses.
- Chlorinated PVC (PVC-C) Pipes: PVC-C pipes are specifically designed to withstand higher temperatures, making them ideal for hot water supply systems and industrial applications. They are known for their excellent heat resistance and chemical resistance.
- Modified PVC (PVC-M) Pipes: PVC-M pipes are a modified version of standard PVC pipes. They are designed to offer improved impact resistance while maintaining the other favorable properties of PVC. They are often used in water distribution and irrigation systems.
- Molecularly Oriented PVC (PVC-O) Pipes: PVC-O pipes are characterized by their exceptional strength and high-pressure capacity. They are used for applications where high pressure and strength are essential, such as water mains, sewage systems, and industrial pipelines.
- Schedule 40 PVC Pipes: Schedule 40 PVC pipes are commonly used for general plumbing and drainage applications. They are lightweight, durable, and suitable for a variety of residential and commercial uses.
- Schedule 80 PVC Pipes: Schedule 80 PVC pipes are designed for applications requiring higher pressure resistance, such as industrial processes and municipal water systems. They have thicker walls compared to Schedule 40 pipes and can withstand greater pressure and impact.
The Different Types of PVC Pipes
Let us now look at the different types of PVC pipes in more details to have an understanding of the properties of each and where each can be used.
1.Unplasticized PVC (PVC-U) pipes
Most of the PVC pipes in the United States are plasticized. What does it mean for a pipe to be plasticized?
Plasticization is the addition of bisphenol A (BPA) and phthalates in the PVC material to help with the flexibility. Plasticized pipes like chlorinated PVC pipes are therefore more flexible than unplasticized PVC pipes.
Flexibility is important for pipes since you can snake it through channels that are not straight. That is however not possible with unplasticized PVC pipes.
This may explain why unplasticized PVC pipes are also known as rigid PVC pipes. These pipes are quite strong especially the schedule 80 PVC-U pipes and therefore have a high impact-resistance.
Apart from their strength, unplasticized PVC pipes have a high corrosion resistance and they tend to maintain their color for a long time despite the weather conditions. This is also another reason these PVC material is very good for window and door frames.
Another advantage of PVC-U pipes is that their interior is quite smooth compared to other PVC pipes. This helps to improve the flow of fluids inside the pipes as there is almost no friction.
Despite their strength, unplasticized PVC pipes are not very common in United States. Plasticized PVC pipes are the most preferred pipes for drain lines.
The flexibility offered by the plasticized PVC pipes makes them popular with plumbers since it is easy to install them in areas where the route needed for the drain line is not straight.
PVC-U pipes are also not used in the transportation of portable water. The material of choice for that other than copper and PEX is chlorinated PVC pipes.
I should however mention that plasticized PVC pipes are banned in Europe and many other countries thanks to the added plasticizers which are potentially harmful. PVC-U is the pipe of choice in those countries.
To read more on the differences between PVC-U and other types of PVC pipes check out this post.
2. Chlorinated PVC Pipes (PVC-C)
Chlorinated PVC pipes are basically PVC pipes with a high percentage of chlorine. This is done in a chlorination process where the chlorine mass is increased from 57% to about 74%, although commercial PVC-C resins contains 63-69% chlorine by mass.
As I mentioned earlier, chlorination of PVC is done to improve its qualities. Importantly, this process is done to increase the pipe’s temperature threshold or heat resistance.
The main difference between chlorinated PVC pipes and other types of PVC pipes is the temperature limit each can reach before softening.
Other PVC pipes have a temperature limit of 140 degrees Fahrenheit while PVC-C can handle temperatures of up to 200 degrees Fahrenheit.
If you are therefore looking to transport hot liquids, chlorinated PVC pipes would be your pipe of choice. Schedule 80 PVC-C are especially great for industrial application since apart from the high temperature limit they can also handle very high pressures.
If you are looking to install a PVC pipe system for water supply, chlorinated PVC pipes are the best. Not only are these pipes durable, they are excellent for transporting both cold water and hot water thanks to the high chlorine content.
Most water heaters are usually set at 140 degrees, the same as the temperature limit for other PVC pipes. With PVC-C’s 200 degrees limit, you will have a safety margin of a whooping 60 degrees Fahrenheit.
One thing that makes PVC-C pipes durable is that they are non-reactive to chlorine (present in the water) while other PVC pipes are. Also, the high chlorine content in the pipes prevents the growth of bacteria whereas bacteria growth is high in other PVC pipes.
Another advantage of PVC-C pipes is that they are available in both nominal pipes size and copper tube sizes, unlike other PVC pipes that are only available in nominal pipe size. This means that you can replace/connect a copper pipe water supply system with these pipes.
PVC-C pipes are also very flexible. As a matter of fact, you will need to support them at intervals of 3 feet.
Check out this post for more information on chlorinated PVC pipes.
3. Molecularly Oriented PVC (PVC-O)
Molecularly oriented PVC pipes are a newer type of PVC that is basically an improvement of the PVC-U. Like its name alludes, molecularly oriented PVC is made by reorganizing the amorphous PVC-U into a layered structure through a mechanical process.
In the manufacture of molecularly oriented PVC pipes, a length of conventional PVC pipe is heated and expanded using high-pressure water. By so doing, a new molecular orientation is achieved where longitudinal molecular structure is reoriented to circumferential direction.
It is therefore important to note the PVC-O is not made by improving the chemical structure of PVC-U (through additional of chemical compounds) but rather by mechanically reorganizing the physical structure of the material.
One of the properties of PVC-O is high impact resistance. These pipes are almost unbreakable. PVC-O pipes also have high stiffness and fatigue resistance, great handling of external loads, maximum ductility and elimination of crack propagation.
A heavy machine can move over a PVC-O pipe and the pipe will not break. It will initially deform due to the weight of the machine but after the machine has moved the pipe will go back to its original shape.
4. Modified PVC (PVC-M)
Modified PVC is an alloy of PVC with an impact modifier that improves the physical properties of the pipe. PVC-M pipes are therefore tough, have a high-impact resistance which prevents the growth of cracks and high ductility as well.
The main difference therefore between modified PVC and molecularly oriented OVC is that modified PVC is chemically altered while molecularly oriented PVC is mechanically altered to improve its qualities.
The impact modifier added to PVC-U to manufacture PVC-M (also known as PVC-HI or High Impact PVC) allows it to be manufactured with thinner walls thereby saving material but with improved hydraulic properties.
In accordance with ISO 6993-1, PVC-HI is how the pipe is labeled and is the only PVC pipe allowed in the transportation of natural gas. These pipes have also been found fit for the transportation of hydrogen.
Schedule 40 vs Schedule 80 PVC pipes
There are 2 main types of PVC pipes when referring to their size. These are schedule 40 and schedule 80 PVC pipes.
Scheduling in PVC pipes refers to the thickness of the pipe. Schedule 80 PVC pipes have thicker walls than schedule 40 PVC pipes.
The reason for having different schedules of PVC pipes is primarily have pipes with different pressure ratings. Due to their thick walls, schedule 80 PVC pipes have a higher pressure rating than schedule 40 pipes of the same nominal size.
Since the wastewater in domestic/lateral sewer lines is not under any pressure, schedule 40 PVC pipes are used to replace or install new drain lines. If you therefore just want to install drain lines at home then schedule 40 PVC pipes are the pipes you should buy.
On the other hand, schedule 80 PVC pipes are mainly used in industrial and chemical applications where fluids are usually at very high pressures.
I have written a detailed guide on the differences between schedule 40 and 80 PVC pipes. Read it here.
And basically those are the different types of PVC pipes. I hope you enjoyed reading this post.