Expansion - Contraction Phenomenon -
Test Method for visual Differentiation
Between CPVC Pipes and PVC Pipes
CPVC pipes are used fo the transport of drinking water. This application
requires that the pipes under normal service conditions can withstand high
internal pressures of water continuously at hot temperatures for 50 years.
For this application, PVC pipes are not approved by any regulatory organism,
because they would fail after very short times under such severe service
This test method describes a simple way to determine with a simple apparatus if
a pipe is made only of CPVC or contains a majority of PVC.
The thermal resistance of CPVC is much higher than for PVC. In terms of
softening point, CPVC pipes are stiff up to 110°C, whereas PVC pipes will
become softer and softer above 80°C. Pipes based on a blend of PVC and
CPVC will show a behavior halfway between these two resins: the higher the
amount of PVC, the softening temperature of the pipe. At a temperature of
100°C (boiling point of water), the pipes containing a majority of PVC
will prove soft, whereas the CPVC pipes will be stiff.
Transparent glass container
No specific hazard
Photo1: Test appartus
sample a pipe (½ inch or ¾ inch Schedule 80)
cut a test specimen from the pipe (approx. 50mm long)
heat the water up to its boiling point (Photo 1)
control with thermometer that the water temperature is higher than
condition the test specimen in the boiling water for 15 minutes
take the specimen off the bath and put it on a flat table
squeeze the specimen manually with a stuff, round-shaped pipe (Photo 2)
The squeeze loading must be applied to the test specimen immediately after it
is taken from the bath, so that it does not cool down significantly.
Interpretation of the Observations
Photo 2:The pipe specimen is squeezed
Photo 3: Pipes containing >50% PVC flatten
This test method is also applicable to fittings (½ inch or ¾ inch
Schedule 80): the injected part is entirely immersed in the water bath for 15
minutes and squeezed on one of its sockets.