From Jay Shelton’s book Solid Fuels Encyclopedia: “For each pound of wood burned with 20 percent moisture content 0.63 pounds of water vapor is generated. … If 50 pounds of wood per day are burned as much as 25 pounds (about 3 gallons) of dirty, acidic, corrosive, smelly water — creosote — will condense.” The chemistry is correct. But the “condense” may be wrong: Condensation will depend on stack temperature.