Which of the following materials is commonly used as a sealant in piping?

Silicone is widely recognized as a suitable sealant in piping applications due to its excellent adhesive properties and flexibility. It effectively creates a watertight seal, making it ideal for preventing leaks in various piping systems. Its resistance to moisture, temperature fluctuations, and UV exposure further enhances its viability, particularly in plumbing, HVAC, and industrial applications where reliable sealing is critical.

The other materials mentioned do not serve the same purpose as sealants. For instance, steel is primarily used for structural support and as a piping material itself rather than as a sealant. Glass, while it can be used in some specialized applications, lacks the flexibility and adhesive properties needed for sealing pipe connections. Polyethylene is commonly used for pipes but is not typically employed as a sealant; rather, it may be joined through welding or fusion methods without needing an additional sealing material.