Underground Installations Can I use hubless cast iron soil pipe and fittings below ground, and is there anything special I need to do to protect the couplings?
Hubless cast iron soil pipe and fittings are allowed for underground installations by all of the model codes. Since the 300 series of nickel chromium stainless steel is even more resistant to corrosion than cast iron, the stainless steel hubless couplings used to join hubless cast iron soil pipe require no more special protection against corrosion than the pipe itself. Even though all of the model codes allow hubless pipe and fittings below ground, a few local jurisdictions have local amendments which require that only hub and spigot be used underground. It is always best to check local amendments. For a thorough discussion of the corrosion resistance of cast iron soil pipe follow this link. For a more thorough discussion of underground installation procedures see Chapter 4 of the Cast Iron Soil Pipe and Fittings Handbook.
