With 3 daughters and a wife all taking showers/baths now our poor little 40 gallon water heater is just not cutting it. So I just purchased a 74 gallon water heater to replace it.
Current Setup: 120,000 BTU gas furnace that has a 4" exhaust pipe. There is about 2 feet of horizontal run before it expands to a 5" pipe. This is where the current water heater exhaust joins in. It then has the 5" pipe that runs another 5 feet of horizontal run before entering into the brick chimney which then goes about 24 feet up to the top of the house.
The current water heater (40,000 BTU) has a 3" exhaust that joins in with the furnace exhaust where it jumps to 5". The new water heater is 74,000 BTU and requires a 4" exhaust pipe. The 5" that runs to the chimney doesn't seem like enough exhaust throughput to support both the furnace and new water heater.
Will I still be ok with this? Does the 5" exhaust need to be changed to a 6" exhaust? Where the 5" goes into the chimney does the tubing continue to the roof typically or does it end and the exhaust goes up the standard chimney liner?