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NGuy 08-07-2008 09:13 PM

Type B Vent Question
I'm in the process of installing a tankless water heater in a small cabin. The cabin is 24 ft wide and 36 feet long with a 4/12 pitch metal roof. I'm looking for advise on running the Type B vent pipe. Please bear with me as I try to explain the position of the water heater in the cabin.

The cabin has two rooms. The main room has a cathedral ceiling and the bedrooms have a flat ceiling (and thus an attic). The water heater is on a wall that is under the cathedral ceiling but is within 18 inches of the transition from cathedral to flat ceiling. The water heater is about 4 feet from the exterior wall, which is the long wall of the cabin, or the eave side of the roof.

I know I can run the vent pipe nearly straight up from the heater but an afraid that in the snow country in northern Wisconsin, I may have problems with the snow sliding off my metal roof and pounding the vent stack.

In order to get the stack to exit closer to the ridgeline of the roof, can I run the stack as follows or will this cause me problems with draft?

- Run straight up from the water heater 20 inches,
- Elbow at 45 or 60 through the cathedral ceiling into the attic above the flat ceiling for about 2 feet,
- Elbow at 45, following the 4/12 pitch towards the ridge line of the roof for about 6 to 8 feet,
- Elbow at 45 to exit through the roof.

I attached two rough drawings to help illistrate what I am talking about. The red circles represent the area where the stack would be nearly horizontal for about 2 feet as it runs through the transition from the cathedral ceiling into the attic above the flat ceiling.

Thanks a bunch for any input!

8 Ball 08-07-2008 09:31 PM

What is the manufacturer and model number of the heater?

NGuy 08-08-2008 09:18 AM

It's a Bosch 1600 P (LP). Sorry about not posting the diagram but I'm having a hard time getting a small but clear drawing.

NGuy 08-08-2008 10:14 AM

2 Attachment(s)
Here are the rought drawings I talked about. I hope this helps to explain what I was describing. Thanks again.

8 Ball 08-08-2008 08:04 PM

After reading the manufacturers instal guide, as long as that 2ft section is pitched 1/2 in, and you maintain the proper clearances, it should be good.

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