Post #9169

When penetrating a wall for a flue pipe, tilt the bit that goes thru the wall downward slightly. All other horizontal runs of a flue should "run" up or level. Only the last bit sticking thru the wall should go downward, and never more than 1/4 the diameter of the flue. LP gas will cause water to condense in the pipe and 1) you need that water to run out, 2)water raining on the house of the house might run into the wall along the flue, so tilt it slightly down. Never underestimate the ability of water to condense in a horizontal pipe. A 12" vent pipe with a 150' horizontal run in a paper mill would exhaust warm moist air out of a piece of equipment. Water would "pond" up in the pipe and when the blower was shut off, all that water would run back into the fan housing. Gallons of water along that 150' run. Always install water traps on long horizontal runs of piping.