Is there any online charts that anyone knows of for sizing flues ( not the chimney) based on btu's? I know it's in the code book, but I don't have access to one recently my copy got "vanished". It's just something my boss said he was going to start asking in our meetings, asking people questions related to gas sizing and water heater flue sizing questions. I'm not a full journeyman.....yet.
In one state you have to upgrade the flue to 4", in another you can still use 3" on like a 50 gallon gas. Does anybody know why there's this difference?