Does anyone know what the min clearance for DuraBlack single wall pipe is to drywall? The specs say 18 inches away from any combustible, but doesn't say what it is for drywall.
Thanks.

18 inches clearance to combustibles for single wall pipe be it for oil or wool/coal burning is code. Drywall is considered a combustible since it has a paper back and has no heat reflective properties.

If you need to reduce clearance you can use another piece of single wall pipe but you leave it open and not locked closed as you would to use it for pipe. You use this as a shield and is allowed by the clearance reduction section in the mechanical code.

Space the unclosed pipe one inch off the other pipe using non combustible spacers (cut them off 1/2 inch copper tube or other metallic tubing).

Run sheet metal screws through the shield through the one inch non combustible spacers and into the original single wall pipe. This makes a metallic reflective surface that prevents the heat from getting to the combustible surface.

You may ask why all of this concern. A out of control oil or wood/coal fire can turn the original pipe cherry red and at a temp of up to 2000 degrees with the creosote burning inside. At that temp anything with in 18 inches that is combustible will combust. That is the reason for the 18 inch rule and that is why the clearance to combustibles shield works because it reflects the heat back to the source and does not allow it to spread out and catch combustibles within the 18 inch clearance on fire.

Hope this help.