Looking for advice on how to eliminate condensation in a flue pipe for a 40 gal. residential hot water heater. Current configuration is as follows: 3" galvanized flue pipe approx. 32" connects draft hood of tank and connects to a 3" I.D. heavy pipe (maybe steel or cast iron) which penetrates finished interior ceiling, through unheated attic crawl and the roof. Pipe extends approx. 24"-32" above roof line. All pipe is vertical. Condensation forms in heavy pipe and pours down onto tank in significant amounts. Can flue pipe be re-done to avoid this problem and what materials/configuration would solve the problem. Told customer we may have to replace tank with power vent type out the sidewall of the house.