Gas Furnace/Water Heater Venting

[Hubert A. Miles]

I have a question about how I should write this up. We don't find a lot of gas furnaces and water heaters in the south. I ran across a gas furnace in a crawl space today. The vent pipe fed into a masonry chimney. In the garage a gas water vent also vented into the side of the chimney above the furnace vent. I believe the two are tied together but can't confirm because it is behind the masonry. Out of the top of the chimney is a single metal flue.

Any thoughts?

[Joseph Hagarty, CMI]

General Notes:
- All Chimneys and Flues should be inspected and swept on an annual basis with use.
- It is recommended that a Level 2 Inspection of the chimney / flue be conducted at this time (prior to closing) in accordance with the NFPA standard. 　

[Charley L. Bottger]

I occasionally see double wall class B running the full length of a non-lined masonry chimney which is allowed in this State

[Bob Elliott]

I would call out the flex going through the knockout and recommend a better support strap for tht B vent as they are using wire.

[Christopher Currins]

Is the vent pipe running downhill?

[Robert Ernst]

If it's vented into the chimney it's not allowed and the appliances should be checked for spillage. If the pipe is using the chimney as a chase that's fine but there is often sheetmetal to close off the top of chimney and prevent debris and moisture from getting in.

[Cameron C. Anderson]

As far as the flue is concerned you can't report on what you can't see. There is either a wye-connector and a metal flue running the length or there is not, but you can't confirm it either way.

I think the most you could say is, (assuming this is true) "Cannot confirm proper venting of combined furnace and water heater. This is not a common installation in this area of the country and I recommend further evaluation to verify proper venting of gas burning appliances through the chimney."

And you could also say nothing, or "Chimney flue not fully visible."

[Charley L. Bottger]

Originally Posted by canderson5

As far as the flue is concerned you can't report on what you can't see. There is either a wye-connector and a metal flue running the length or there is not, but you can't confirm it either way.

I think the most you could say is, (assuming this is true) "Cannot confirm proper venting of combined furnace and water heater. This is not a common installation in this area of the country and I recommend further evaluation to verify proper venting of gas burning appliances through the chimney."

And you could also say nothing, or "Chimney flue not fully visible."

If one owns a CO meter ya can confirm from the roof proper venting