Chimney Cleanout - Part III

Depends on how efficient it is. Some of the highest efficiency ones don't have a flue at all, they have to be vented with a plastic or other corrosion resistant pipe that is sloped in such a way that it drains outside.

No, it makes perfect sense. One of the byproducts of combustion is water. While the cap on top keeps critters out, it also makes a cold spot for the vapor to hit, condense, fall to the bottom in the form of water.

Burn wood too cool and you can get puddles of water as it has a higher water content.

If you d "If it's not rain, it could be condensation caused by the flue, which is also not a good thing."

Moreover, condensation would cause dampness, not rivers of water.

BTW...why do you keep starting new threads instead of keeping this single subject contained in one so that it is easier to follow?

Well if you replace the furnace you can vent via schedule 40 PVC pipe, then you can abandon the chimney altogether. You can also not worry about the dampness in the chimney and let the next home owner worry about it's effects on the mortar and bricks.

Burn wood too cool and you get creosote build up. Chimney fires are "exciting" I'm told.

Is this an open flue with the HE furnace just dumped into it? If that's the case, it's perfectly reasonable (and, at least here, not allowed for anything that isn't a natural draft furnace).

It's a bad idea even if it is/was allowed there at the time it was done...using a double-walled riser would solve the problem as they say it 'twould.

If it's just a single-wall ducting inside the existing flue, then it's true will likely be getting condensation before it all gets out the top, but most of that's going to run back down the flue itself because the air still hasn't exited.

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