What is the primary substance used to protect listed CPVC sprinkler systems from freezing?

The primary substance used to protect listed CPVC (Chlorinated Polyvinyl Chloride) sprinkler systems from freezing is glycerin. This is because glycerin is a non-toxic, biodegradable liquid that remains fluid at lower temperatures, making it an excellent antifreeze agent for systems that may be exposed to freezing conditions. Its properties allow it to lower the freezing point of water, thus preventing ice formation within the sprinkler lines.

Glycerin's compatibility with CPVC materials is another important factor. Many antifreeze solutions can be corrosive or damaging to certain types of plastics, but glycerin is safe to use with CPVC, ensuring the integrity of the sprinkler system is maintained.

This choice is informed by standards and guidelines in fire protection systems, emphasizing the importance of using substances that are safe for both the materials involved and the environment when it comes to fire safety systems.