PVC Pipe Temperature Ratings – Don’t Melt Your Pipes!

There’s something we always ask the engineers, purchasers, pipe-fitters, and contractors who source their PVC pipes, PVC pipe fittings, and piping accessories from us at Polyfab Plastic Industry LLC: What will the operating temperature be in your piping project?

Polyvinyl chloride, or PVC, is a strong and durable material with excellent resistance to abrasion, corrosion, and many chemicals. Thus, it is a top piping option in municipal works and construction, particularly in mechanical, electrical, plumbing, sewage, and drainage applications.

However, you must not forget the PVC pipe temperature rating, particularly the maximum temperature PVC pipes can withstand before they begin to change or their desirable properties begin to weaken.

Why PVC Temperature Rating Matters

Take it from us. For nearly two decades, we have been supplying the United Arab Emirates and the rest of the region with plastic drainage pipes, infrastructure pipes, and fire-fighting pipes. We also have considerable experience providing contractors with pipe fitting and  installation support.

PVC pipes are created by heating the PVC polymer to a certain temperature until it’s soft and pliable, at which point it is extruded or injected into a mold. PVC is classified as a thermoplastic for this reason. Thermo for heat, plastic for plasticity or moldability — it means thermoplastics like PVC become moldable with heat. This is why the PVC temperature rating matters.

Is PVC heat resistant? Yes, but only up to a certain point.

PVC is a hard and durable material only within a particular temperature range. Beyond a certain temperature, PVC becomes pliable and loses the strength and durability it is prized for. Therefore, use PVC pipes only within their set temperature limits.

What Is the PVC Pipe Temperature Rating?

What temperature can PVC pipe withstand — i.e., what temperature is PVC rated for? The typical maximum operating temperature of PVC pipes is 60 °C (140 °F) if without pressure and 38 °C (100 °F) in pressure applications. PVC pipes have a maximum short-time operating temperature of 95 °C (203 °F).

What temperature can PVC withstand before it becomes distorted? It’s 54-80 °C, the typical heat distortion temperature of PVC pipes. At this particular temperature, PVC pipes attain a specific deflection upon applying an 18.6 kilogram per square centimeter of bending load.

Deflection, also known as ovalization, is the percentage change in the pipe’s vertical diameter caused by applying a vertical load. It happens when the pipe’s vertical diameter decreases while the horizontal diameter increases.

PVC pipes also have a Vicat softening temperature (VST) of 92 °C (197.6 °F). This VST corresponds to the temperature at which the pipe is soft enough to allow a needle-shaped indenter with a cross-sectional area of 1 square millimeter under a vertical load of 1 kg (10 newtons) to penetrate the pipe to a depth of 1 mm.

Use the above temperature ratings as a general guideline for determining PVC pipe’s suitability for your particular application. Note these are typical figures. A PVC pipe’s actual maximum operating temperature can vary according to dimensions and specific formulation.

For instance, a pipe with a bigger schedule (wall thickness) may have a higher PVC heat rating than a smaller schedule pipe. As a case in point, the recommended schedule 40 PVC temperature rating is 54.4 °C (130 °F), while the suggested PVC maximum temperature rating for schedule 80 pipes is 60 °C (140 °F).

The Melting Point of PVC Pipe

At what temperature does PVC pipe melt?

Melting is the breakdown of a crystalline structure culminating in molecules or atoms separating from each other. In this light, semi-crystalline plastics like high-density polyethylene (HDPE) can melt, although at very high temperatures (148.89 °C or 300 °F), thus the suitability of HDPE pipes for fire-fighting and other high-temperature applications.

PVC is an amorphous plastic, not a semi-crystalline material like HDPE. This is why, technically speaking, PVC doesn’t melt.

Thus, when some people talk about the melting point of PVC pipe, they are probably referring to PVC pipe’s glass transition temperature. This is a range — 100 °C to 260 °C (212 °F to 500 °F) — and it is the temperature at which PVC pipes transform from hard and rigid to soft and pliable.

Note that the actual melting point of PVC pipe varies according to formulation. For instance, the melting temperature range for flexible pipes is 100-150 °C (212-302 °F). Chlorinated PVC (CPVC) pipes, which have undergone an additional chlorination process to make them more rigid and more tolerant of higher operating temperatures, may have a melting temperature range that starts at 220 °C (428- °F).

The Implications of PVC Temperature Rating

The PVC pipe temperature rating answers this question: How hot can PVC pipe get before its properties change? Asking this question is crucial because you need to know how much strength and resilience you can expect from your PVC pipe, given your particular application’s operating temperature.

You see, published pressure ratings, stiffness ratings and pipe dimensions are obtained at a temperature of 22.78 °C (73 °F). If you’re using PVC pipes at temperatures that fall below or above that temperature, you must adjust your expectations regarding your pipes’ capabilities.

1. Length

PVC expands as the temperature rises and contracts as the temperature falls. Consequently, the higher the temperature, the longer PVC pipes become.

Remember to account for the operating temperature range — the highest and lowest temperatures possible in your particular application — when installing PVC pipes and conduits. The rule of thumb is to allow for a 0.9525 cm pipe length variation for every 5.56 °C change in temperature.

2. Pressure Capacity

The higher the temperature, the lower the PVC pipe’s ability to withstand pressure. The lower the temperature, the higher its pressure capacity. Remember this when using PVC pipes for high-pressure, high-temperature applications.

As mentioned above, published pressure ratings are derived at a standard temperature of 22.78 °C (73 °F). If you’re using a pressure-rated PVC pipe at operating temperatures higher than 22.78 °C, make sure to adjust the pipe’s pressure rating accordingly.

Note that at the maximum operating temperature of 60 °C (140 °F), PVC pipes are 78% weaker than their standard pressure capacity.

3. Stiffness

The higher the temperature, the less stiff PVC pipes are, and the lower the temperature, the stiffer they become. Stiffness pertains to the pipe’s ability to resist deflection or ovalization under load.

Note that at the maximum operating temperature of 60 °C (140 °F), a PVC pipe is only 70% as stiff as the standard stiffness rating derived at 22.78 °C.

What Temp Can PVC Handle?

PVC is a stiff, strong, and durable material favored for its excellent chemical, abrasion, and corrosion resistance. However, you can’t use PVC pipes haphazardly, especially in construction projects, without first checking their temperature rating.

Additionally, unless your operating temperature is consistent at 22.78 °C, you cannot take your PVC pipes’ dimensions, pressure capacity, and stiffness rating at face value. You must derate the published standard ratings according to your site’s actual operating temperature ranges to ensure you know the actual capacity of your PVC pipes and conduits.

Polyfab Plastic Industry LLC is a trusted manufacturer and supplier of PVC pipes in the UAE. Contact us if you need to source high-quality PVC pipes manufactured according to internationally established pipe manufacturing standards or require pipe fitting and installation help for your project.