Polyvinyl chloride or PVC pipes are the cornerstones of many of our homes. As a thermoplastic material, they are superior to copper pipes in many ways and are used to carry essentials such as water, sewage, electrical cables or to ventilate hot air.
PVC pipes are cheap, easy to shape and even easier to install. They seem to be the perfect equipment. But, unfortunately, there is one factor that you have to consider – temperature.
The pipe can only maintain a certain temperature before it suffers structural and integral damage. If you’re wondering what temperatures your PVC pipe can withstand, we’re here to help.
This article will detail the specific requirements of PVC pipes, including advice on supporting them during extreme temperatures. We’ll also explain how to protect your pipes, what signs of stress you should look out for, and alternatives you can consider.
What temperature can PVC pipes withstand?
What is the maximum temperature that PVC pipes can withstand?
Simply put, the maximum operating reference temperature of a PVC pipe is 140°F (60°C). This temperature makes PVC an ideal material used to transport a variety of cold materials, such as water and sewage, both domestically and industrially.
140 is the upper limit, but there are a few things to watch out for in how the pipe handles the temperature rise. Consider the pipe size (schedule) and its operating pressures (PSI), as these two can contribute to how your pipe performs under stress.
As the temperature increases, the amount of pressure the pipe can withstand decreases. A typical example to illustrate this point is the standard 6″ Schedule 80 PVC Pipewhich typically has a PSI of 280. But when operating at the maximum temperature of 140°F, the PSI drops to 62 (280 x .22).
How cold can PVC pipes withstand?
Because PVC pipes are so versatile, many people use them to carry water outside for gardening, to connect to external sewer lines, and more. But if you live in a colder climate or are concerned about winter and a frozen environment, you may wonder if cold temperatures can adversely affect PVC pipes.
The drop in temperature can contract plastic pipes, reducing their «impact resistance», while the pipes should be able to function normally, this becomes very important if PVC pipes carry water that has the potential to freeze.
Water expands when frozen and can press on already fragile pipes and joints. The constant freezing and thawing action can the buckle of the pipes, their cracking and fracturing and creating a series of leaks in your system. One way to counteract this problem is to use thicker pipes.
Another problem you may encounter with extreme cold is during incorrect installation. Loose fittings can allow water to seep in and subsequently freeze. A great tip to keep in mind when installing PVC pipes underground is to keep pipes and chicken necks at least 12 inches below freezing depth to protect the most vulnerable parts of the plumbing.
Does the temperature of sunlight affect PVC pipes?
If you live in a hot climate or if summer is fast approaching, you may be concerned about temperature changes due to prolonged exposure to the sun. After all, direct sunlight is known to erode many different materials over a long period of time.
The good news is that most PVC pipes are made from UV-resistant materials, which means they won’t expand or break during direct or prolonged exposure to the sun. The only consequence may be a gradual discoloration over time. This means that PVC pipes can be used to connect irrigation systems, as a drain, for gardening or for outdoor plumbing.
If you doubt the properties of your PVC pipes, you can cover them with simple water-based paint, which acts as an additional layer of protection. Use light or white paint to repel UV rays and avoid oil or solvent based paints as they can damage plastics.
Thermoplastics – why PVC changes at high temperatures
To understand how PVC changes with heat, you first need to know how it is made.
PVC is a synthetic polymer that can be easily molded into various shapes at high temperatures. Chemicals like chlorine provide fire resistance and PVC has natural corrosion resistance properties.
At high temperatures, PVC can be remodeled. While this makes it a dream material to use in the manufacture of various pipe parts, shapes and sizes, it also means that it always has the potential to structurally change under extreme heat when installed in your home.
You should avoid using PVC pipes to transport boiling material such as hot water, as this may cause an explosion or sudden fracture of all or part of the pipe. In the video below, you will see how heat can affect the pressure capacity of a PVC pipe:
Signs of temperature damage in PVC pipes
Understanding how temperature affects PVC can help you decide where to use this type of plastic, but it also allows you to spot any signs of potential damage. This is especially the case if the pipes are above ground and visible.
Three critical areas affected by temperature fluctuations include:
1. Rigidity of the pipeline
PVC pipes are known as flexible pipes, which can yield under load «no fracturing». They can comfortably divert excess material without any pressure on the overall structure of the pipe.
That said, research has shown that an increase in temperature can have negative effects affects stiffness by up to 80% in PVC pipes, rendering their innate flexibility useless. This dramatic loss of rigidity can mean pipes lose their structure and risk disconnecting from the rest of the plumbing system.
2. PVC dimensions
Dramatic changes in temperature can affect the dimensions of PVC pipes, including their length. Some experts say the changes can be as much as 3/8″ every 100 feet of piping. It can take up to a 10 degree change in temperature (both warmer and cooler) for this to happen.
This can be quite alarming to happen, especially if the dimensions of the plumbing pipes change. Consider using ground-penetrating radar (GPR) to detect breaks if your pipes are underground, behind walls, or submerged. And finally, avoid any drastic changes in temperature as a preventative measure.
3. Pressure assessment
The pressure rating of PVC is temperature dependent, with the standard duty rate measured at 68°F (20°C). As the temperature rises, you should reduce the working pressure of PVC pipes. If the temperature drops to freezing, avoid damaging the pipe during its weakened state. This helpful guide helps to explain the maximum working pressure for PVC pipes in relation to temperature.
Do you need to reach a higher temperature? A CPVC pipe
Let’s say you want a pipe that can withstand higher temperatures than those listed above, such as a hot water pipe for your home or business. You may need to consider a different thermoplastic with a maximum allowable operating pressure higher, such as chlorinated polyvinyl chloride (CPVC).
CPVC is similar to PVC except that it has a different chemical composition in production, namely additional chlorination. This allows it to withstand temperatures up to 200 °F (93 °C). To combat these extreme temperatures and ensure safety, CPVC has natural flame retardant and chemical resistance properties instilled into it during production.
In addition, CPVC performs better than PVC in PVC’s natural temperature range, making it the superior choice for many different purposes. But of course, it is much more expensive than PVC, which you have to consider.
Most of the time, CPVC is perfectly safe for drinking water drainage and can even reverse the effects of the chlorinated water found in our home faucets. But to be sure, check the manufacturer’s instructions.
Conclusion
PVC is a versatile material used in many, if not all, constructions. It can carry a variety of materials effortlessly and when well cared for can last up to 50-80 years. Talk about great value for money.
But melting temperatures are a difficult challenge for PVC, and pipes will often break or warp when exposed to rising temperatures. Dimensions and overall structural integrity will suffer significantly.
The best way to ensure that your PVC pipe remains in pristine condition is to plan its purpose accordingly. Temperatures can fluctuate, so it’s best to use PVC only when the liquid or material never reaches 140F.
If you have any more questions about PVP piping and the temperatures it can reach, please leave a comment below. But when in doubt, always remember:
- PVC is a thermoplastic that can withstand 140 degrees F (60 °C)
- That being said, extreme hot and cold temperatures can affect the structure of a PVC pipe
- Always check the manufacturer’s instructions, including the pressure level, for guidance
- A CPVC pipe can reach higher temperatures than PVC, ranging from 180-220°F
