rekoj71 wrote:
I use the rain gutter down spout set up exactly as Ivylog has pictured.
"Exactly as pictured" there is an engineering problem.
Expecting the exhaust pressure to jump an open horizontal gap is iffy at best. It won't take much of a side wind to deflect part or most of the exhaust OUT of the extension pipe.
The sealed exhaust pipe should turn upwards before the gap and should be even with the extension pipe or slightly inside. Too large a gap will allow for too much disruption of the convection flow.