Hey guys, I saw the homeowners upgraded their water heater to a high-efficiency tankless unit. They decided to run the PVC vent about a quarter of the way up the original 10+ foot metal flue. Is this acceptable? Thanks, everyone.
That’s a no. The flue gasses might not be hot enough with a HE unit to continue upwards and exit the home.
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Good eye Yu; nice observation.
I was thinking the same thing Ryan, thanks for confirming.
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No, No and No
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I would write it up as an improper installation and recommend corrections be made by a qualified plumbing contractor. The PVC vent pipe should terminate to the exterior.
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Definite NO! A non-condensing furnace relies on the heat of exhaust to create a draft up the flue. S In your situation, condensing furnace, practically all of the heat has been removed from the exhaust there will be little or no draft. Same with a water heater. In fact cold air in the flue (from periods in between operation will push the exhaust into the living space - backdrafting! This is a dangerous situation.
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Refer to the manufactures flue instructions.
You test for CO?
PVC not sealed to metal flue. Down drafting would be hazardous to the occupants.
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Thank you for all your responses guys; you make me a better inspector by the day.
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- The combustion air is coming from the home interior (see top LH side of water heater).
- The combustion supply air and combustion exhaust termination should both be at the same location; adjacent on an outside wall, adjacent on the roof.
- Existing metal pipe, if not aluminum, will rust from high water content of exhaust gasses.
- Refer client to manufacturer installation instructions for correct installation.
I would have to disagree with this somewhat. Most HE appliance manufacturers allow for a non-direct vent installation. Below is a picture from a Navien tankless w/h install manual. Although direct vent is recommended, it is not required. I see quite a few HE appliances not direct-vented in my area.
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