Tempstar
Flue Condensation
Water dripping from metal flue pipe on a standard-efficiency Tempstar furnace.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Undersized or uninsulated flue, Long horizontal flue run, Low return air temperature, Incorrect furnace sizing
How to Fix / Troubleshooting
Safety: Flue gases contain carbon monoxide. Do not modify venting without following code and manufacturer guidelines.
- Step 1 – Inspect flue connections: Check for loose joints or gaps where condensate can escape. Reseal with high-temperature sealant where appropriate.
- Step 2 – Check slope: Ensure the flue slopes upward toward the chimney or termination at least 1/4 inch per foot.
- Step 3 – Improve insulation: In unconditioned spaces, consider insulating around the flue (per code) to reduce condensation.
- Step 4 – Professional evaluation: Have an HVAC professional evaluate vent sizing and furnace operation to reduce condensation formation.
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Repair Difficulty
Hard
4/5
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