[amakarevic]

on its way from a gas appliance (water heater and boiler), i was wondering if it is acceptable for the exhaust duct to ever change elevation negatively or is that some sort of a no-no, like it is for a drain vent pipe to do the opposite (go up)? i was wondering if that might be a CO hazard or something like that.

basically, my gas heater alcove is on one side of a narrow (12 ft) passage while the chimney is on the other. i want to run the duct up to the ceiling, reach the other wall, and then descend a little bit to reach the chimney entry. well, this descending is what worries me whether it is OK. if not, i may have to drop the ceiling to be lower than where the chimney starts.

thanks

 

[beenthere]

Its a no no.

It won't draft right, and can cause CO to be expelled into the home.