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When a vent is less than 10 feet high, the vent should be at least as large as the flue collar outlet.b) Vents for draft hoods or flue collars 12 inches in diameter or less should NOT be reduced more than one pipe size.
Valves and connections and. where the pipe passes through walls and floors are good places for the identifying color. The color band should be at least 8â long for. small diameter pipe and increased for larger pipe, up to 24â for 10â pipe and 32â for sizes over 10â diameter.