You should be able to send a camera down the flue to see if there is cross conections. Or you could try dropping a shop light on a cord down one flue while you look down the other flue to see if light comes though. Probably work better at night.

If you only had a fire going in one flue I suspect your problem could have just been a cold down draft sucking the smoke back into the house. The fire would have made this even worse. As the smoke goes up the chimney it draws air with it. Air needs to re-enter the house and often the other chimney is a good location for this.

[This message has been edited by joed (edited October 02, 2003).]

Way too expensive, geeze you could build a new chimney for that price. Liners to consider are made of stainless steel for wood burning fuels, and aluminum for natural /propane.

$4,000 isn't a fair price? That's what two different estimators independently told me. We are talking about relining TWO different flues... but I suppose another estimate wouldn't hurt.

Actually, the problem may not be related to the chimney liner at all.

It is VERY common for side by side flues to have this problem even when the flues are intact.

The problem is usually that when one fireplace is operating it is much easier for 'fresh air' to be drawn into the house via the other fireplace than from anywhere else in the house.

The result is that the unused flue sucks smoke into the house as well since it is so close to the other.

The simple solution in this case is to keep a window cracked in each room where the fireplace is being used.

That way fresh air comes in from the window, not down from an adjacent flue.

I would agree with those who are postulating that there is fresh air being drawn into the downstairs chimney... except for the fact that the downstairs chimney has not one but TWO dampers -- a top damper (at the top of the chimney) and one right above the fire box.

So it would seem that it's unlikely the smoke is being sucked in from the top of the chimney and heading two floors down, wouldn't it?

Where does it ever say that the downstairs chimney has two dampers? One at the top and one at the bottom of the chimney?

Not making sense to me that claim.

I'm not sure why you ask, "Wherever does it say" that the chimney has two dampers... Trust me, it has two dampers. The top damper was clearly put in later than the other one (to keep out critters). I've got a chain at the bottom of the chimney that operates the top damper and a lever that operates the damper at the bottom of the chimney.