[Alumifab]

Do you seal the gas furnace pipe vent with tape or mastic or leave it alone?

 

[WhatRnsdownhill]

if it is a natural draft, no, just screw each section of pipe together so it wont fall apart. if its an induced draft vent, yes, but most new units have special stainless flue pipe that comes with internal seals and clamps already on the pipe to hold sections together..

 

[Alumifab]

ok how do I know if it's a natural draft or induced?

 

[WhatRnsdownhill]

the unit will have a fan for induced draft...to force the flue gas out of the unit..

 

[Alumifab]

Yes, there's a fan.
I have some aluminum tape I'll put on the 2 joints in the above pic.
Thank you.

 

[WhatRnsdownhill]

it wouldnt hurt to do the flex joints in the elbow while you have the tape out...

 

[ben's plumbing]

that is double wall b vent pipe....some wrap joints ..some don't....