Thread: Inline Vent Connectors

Two of the houses I inspected this week had vent connectors for natural gas fired appliances installed into a masonry chimney inline with each other. As a rookie I'd like to make sure I'm interpreting not only the IRC correctly, but that I'm correct in calling these out as safety issues/defects which should be corrected.

Here's my comment and the illustration I include next to the picture....Is this both technically accurate and in your opinion are we justified in calling these installations out for correction in 25 + year old houses?

Building standards state that vent connectors from separate appliances connecting to a shared chimney shall be offset such that no portion of one vent connector's inlet, at the chimney, is opposite another inlet. This requirement ensures the draft of one appliance does not impede the proper draft of another appliance. Improperly vented fossil fuel burning appliances may experience incomplete venting of exhaust gases, which may result in toxic carbon monoxide being introduced into the living space. The vent connectors for the water heater and furnace are inline with each other in violation of this building standard. This is considered a defect which should be corrected by a qualified, licensed contractor.　

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The flues, while entering at approximately the same height are not opposite each other in the first picture.

Your response is accurate as I interpret it.

Ashley Eldridge
Chimney Safety Institute of America
Director of Education

What was the plate covering? Different color concrete + cracks + bad flu + spackle..

Inquiring minds want to know.

John-

Originally Posted by John Armstrong

What was the plate covering? Different color concrete + cracks + bad flu + spackle.. -

Probably another opening into the chimney. I would guess it was filled in, and that was just "decorative." ;-)

I've seen those before in houses that used to have free standing stoves, or wood stoves in the kitchen, etc.

Originally Posted by Kary Krismer

Probably another opening into the chimney. I would guess it was filled in, and that was just "decorative." ;-)

I've seen those before in houses that used to have free standing stoves, or wood stoves in the kitchen, etc.

Those "pie plates" are often no more than a cover for the hole where an earlier appliance connector entered the flue. Having all three openings at the same height suggests that the flue may not go any lower. Ideally, the smaller connector enters the chimney (with sufficient clearance to the floor joists) above the other. A clean-out should be installed at the base of the chimney and the unused hole bricked up tight.

Ashley Eldridge
Director of Education
Chimney safety Institute of America

Thanks for the replies.

AD....good eye, both houses had improperly sloped vent connectors

David....you've mentioned my concern in interpreting the code section. The difference, if any, between inline, opposite or at the same level. I think the draft dynamics of all three would be similar and warrant the same concern so I don't think it matters, but the code should be worded with more clarity IMO.

John & Kary...the plate was covering another thimble and yes, it was filled in...see attached pic.

Ashley....you're right, the flue in the second house/pic did not go any lower and the pie plate covered opening was the defacto cleanout.

Does anybody consider those spring loaded pie plates a suitable cover? 98% of the time I see either the pie plates, which seem insufficient to me, or mortared up thimbles, which seems too much to me, because needs and appliance configurations change over a house's life cycle. There should be a commercially available middle option where it's properly sealed and air tight, but relatively easy to remove to accommodate future changes and or periodic cleaning/checking of the flue. There must be something like that around, but except for a few custom made covers I've never seen one.

Originally Posted by Robert Foster

Thanks for the replies.

AD....good eye, both houses had improperly sloped vent connectors

David....you've mentioned my concern in interpreting the code section. The difference, if any, between inline, opposite or at the same level. I think the draft dynamics of all three would be similar and warrant the same concern so I don't think it matters, but the code should be worded with more clarity IMO.

John & Kary...the plate was covering another thimble and yes, it was filled in...see attached pic.

Ashley....you're right, the flue in the second house/pic did not go any lower and the pie plate covered opening was the defacto cleanout.

Does anybody consider those spring loaded pie plates a suitable cover? 98% of the time I see either the pie plates, which seem insufficient to me, or mortared up thimbles, which seems too much to me, because needs and appliance configurations change over a house's life cycle. There should be a commercially available middle option where it's properly sealed and air tight, but relatively easy to remove to accommodate future changes and or periodic cleaning/checking of the flue. There must be something like that around, but except for a few custom made covers I've never seen one.

There are actually UL Listed "plugs" designed for that purpose. While it may seem to be an advantage I suspect that changes to the venting are not made that frequently. The advantage would be to present a smooth face to the interior that simple brick and mortar would not be likely to do.

Ashley Eldridge
Director of Education
Chimney safety Institute of America