Arrived onsite for no hot water from high efficiency combo boiler…observed code 603. Performed diagnostic for clogged condensate and blocked flue pipe. Checked all area of condensate drain pipe. Poured water and confirmed proper elimination of water. Upon start up hearing gurgling noise. Contacted manufacturer Tech Support performed trouble shooting. Removed flue exhaust pipe and was able to get system to fire up without gurgling. Customer mentioned the rood was recently replaced. Went to the roof inspect exhaust. Checked attic and found pitch of the flue pipe was creating water trap and not allowing flue gases to escape.
