I used a sealed transition from a metal gas water heater exhaust to a ceramic chimney inlet. After examining for a natural gas leak, the examinee noticed that the oval ceramic chimney inlet between the smaller round metal flue on my gas water heater did not seal properly. The old sealing was applied dry and could allow exhaust fumes to penetrate into the basement through these joints. The inspector recommended the use of high-temperature sealants for high-temperature furnaces and flues or high-temperature tape. I chose duct tape as it should never dry out. I also sealed the unsealed connections in the water heater exhaust pipe. I recommend.
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