| You can use mastic, silicone or electrical putty. You cannot have any inaccessible fittings. It must be one pipe, with access to both threaded ends when complete. CSST was created for these situations and would be a better choice. However, if you use CSST, you have to bond the iron pipe where it enters the building to the electrical bond at the panel. This requires a minimum #6 copper wire and is needed to protect the CSST from potential lightning strikes. |