When can plastic piping terminate above grade?

Plastic piping can terminate above grade when an anodeless riser is used, as this configuration is specifically designed to transition from underground plastic piping to above-ground installations safely and effectively. Using an anodeless riser helps to mitigate risks associated with corrosion that can affect metal components and creates a reliable seal that prevents leaks. Anodeless risers are unique because they do not require a traditional metallic fitting that could be susceptible to corrosion or other forms of degradation over time.

This option aligns with safety standards and guidelines within the National Fuel Gas Code, which emphasize the importance of proper connections and the prevention of potential leaks or exposure to environmental factors. The other options do not meet the code's requirements as effectively, as insulation does not address the specific concerns of transitioning above ground, concealing does not provide a secure or compliant method of installation, and proximity to freezing temperatures brings additional risks that can compromise the integrity of the piping system.