Hey everyone!  First time poster here… I’m looking to repurpose unfinished attic space to create a bathroom, but our existing water heater vent pipe runs up from the garage and through the space we need for the bathroom.  The optimal spot to re-route would only require that the pipe be rerouted a few feet, BUT it would put it into an enclosed area behind framed drywall.  I’m aware of the requirement that double walled vent pipes be more than 1 inch from combustibles and can achieve that. However I’m not clear whether the pipe itself needs to accessible?  Any guidance you can provide here would be greatly appreciated.  Thank you.