Which Way Does That Pipe Go?

A fairly common point of confusion for many stove owners is understanding which direction the crimped end of the stove pipe is supposed to go - toward the stove (down) or toward the chimney (up). 

Back in the old days - say up to about the mid to late 1970's, the convention was for the pipe crimp to point up (crimped-end up).

Then along came 'airtight' stoves - models that were well sealed and would air starve the combustion chamber and therefore the chimney system.  This resulted in a new concern. Because of lower operating temperatures during long burns, there was more liquid condensate formed which not only smelled bad, but was rich in creosote precursors. These 'juices' or creosote (a highly flammable and dangerous combustion by-product) could deposit on the pipe wall interior or even the exterior when the pipe crimps were pointing up. So code officials, safety experts, and manufacturers developed new rules and the connector pipes were pointed down and into the appliance flue collar to contain the condensate to the interior of the appliance firebox.  Since airtight stoves should create a slight negative pressure in the system when properly operating, smoke spillage from seams was virtually eliminated by the infiltration of air. All the joints need to be cemented and screwed together anyway.  So...  since the late 70's, the convention on virtually all wood stoves is crimped end down.