Thread: flue overlap incorrect

Hi Guys,

Looking for a little help here with today's inspection of a fireplace flue. The home is 12 years old, fireplace appears to have never been used. Makes it easy to see this defect. I hope you can see my attachment. It appears that the flue pipes were put togetheback-wardsds - overlap can allow heated gasses in these gaps. At least that is what I'm thinking. Comments appreciated. The fireplace is a Marco 792774E.
Thank you!

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Definitely an incorrect and potentially unsafe installation. Not only are the flue projections a problem, but the numerous dips and doodles of the run will compromise the unit's ability to effectively draw combustion gases out of the room. Did the place have a working CO detector in the vicinity of the fireplace?

Thanks for the feedback and verification of my findings.

No, only smoke detectors in the condo.

Thanks again.

There are other schools of thought to consider, or so I've heard. So please correct me if I'm wrong.

The overlap facing down is intended to prevent condensation from leaking out of the flue and damaging other building materials. The lap in the picture would force condensate to drip into the fireplace instead of into the wall or framed chase.

Also, if sized correctly, there would be a slight negative pressure condition in the flue during use which would prevent gases from getting out of the seams.

Again, please correct me if this makes no sense

John Dirks is correct. First of all, we assume you are shooting that pic up from below?
The pipes are correctly installed to prevent creosote, which is flammable wood tar, from leaking out into the chimney chase, if there is one, or dripping onto the stove.

Bob Harper will confirm this, no doubt.

A few minor bends in the flue are not likely to cause a problem. The old potbelly stoves used to be set in the middle of a room with several feet of horizontal stove pipe going over to the wall.

Solid fuel is always male end down to contain the creosote inside the flue.

On air cooled factory built fireplace chimney elbows, often the male end will actually protrude down appearing to make an improper joint. However, there is a bead rolled into the adjoining section above making for a rather tight seal while allowing thermal movement.

While I cannot see this fireplace from my house, it may be ok. The maximum offset from vertical is 30 degrees. There is one fireplace, the old Heatilator Mark 123, that allows a maximum offset of one 15 degree ell-period.

Recommend level II

Yes, the pic was shot looking up from inside the fireplace. So, this is ok?

It might be if air-cooled mfg chimney for solid fuel, as Bob H. said: "Recommend a full Level II (as per NFPA 211) Inspection" (a minimum recommendation any time property is changing hands, btw.)

We have no idea if a gas log set has been retrofit, we can't see all that would need to be seen (such as Bob H. has already pointed out - the degree and number of offsets - spacing, returning to vertical, etc) and determined, or anythiing else required of a complete Level II.

Thanks guys! I recommend further evaluation.
It's a fireplace insert, no stove. There is no gas on the property, so it would just be wood burning.

Darn me! For suggesting it was an incorrect installation, that is. Learn something new every day. Thanx for setting me back on the straight and narrow.

Interesting that I lived for 7 years in SW Colorado, both in a home having a wood stove (but later converted to propane), and visiting and observing others having wood stoves installed and working--at least one as a sole source of heat. Don't ever recall seeing any that were nested in the direction shown in the OP's photo. I know the place we owned had pipe (lots of it, in a tall A-frame log cabin) nested like water-line pipe, with bell end over spigot end, heading downward. And not a hint of any creosote or condensation ever leaking from any joints. Guess it all depends on the tightness of the individual pipe connections, and whether hot fires were regularly burned (which we always did) to burn the creosote off before it could leak out the seams.

Maybe it's me; does that look like a single wall pipe?

Is this inside a wood chimney chase?

Originally Posted by BridgeMan

Don't ever recall seeing any that were nested in the direction shown in the OP's photo. I know the place we owned had pipe heading downward. And not a hint of any creosote or condensation ever leaking from any joints. Guess it all depends on the tightness of the individual pipe connections, and whether hot fires were regularly burned (which we always did) to burn the creosote off before it could leak out the seams.

Right. A lot of wood stoves are installed by home owners, and the stove pipes don't come with instructions or with arrows painted on them.

Don't feel bad. I thought the same way for many years. Matter of fact, the old cast iron cookstoves and heaters had castings that would only receive the female end of a stove pipe. If you stuck the crimped male end in there, it would certainly belch smoke and everybody would call you an ignoramus.

But the standard and correct way is crimped end down.

While we are on this subject. I saw one that does not look right to me today as well. The only pic that I got was not that great but it shows the baffles where the vent connected to the firebox. I have not seen one like this and it looked to me like it would allow the hot gases outside the chimney. Is there something missing from the connection or is this something that is correct that I am not familiar with?