Ok, where to start?
- It looks like the HWT flues are larger than 4" (typical 40 gallon outlet). Have they been increased down below or is that the picture?
- Is the furnace draft induced or older atmospheric? That would be my primary concern. Furnace may need to be separated out.
- The TEE connections should also be a Y
- Did the flue suck out a match at the HWT hood?
- 200K+ into a 5", 6" main vent? Probably too much. (7 or 8") I know someone here has the chart and will post soon.

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Accurate Inspections & Consulting, Inc.
847/736-9975
Markus Keller