B-Vent is intended for neutral or negative draft applications. It is designed for vertical installations (including laterals) but may be used for horizontal applications with a draft-inducing fan located such that all indoor portions of the vent are under negative pressure.
The maximum horizontal length of a Type B double-wall connector shall be 100 percent of the height of the chimney or vent except for engineered systems.
While you can indeed run a horizontal vent pipe, you can't do it indefinitely; this is designed to provide your pipes with the ability to drain into the sewer system. The typical rule of thumb according to code requires you to run a horizontal pipe for no more than one-third of the total length.
Gas Vent Connectors
Double-wall corrugated aluminum with B vent ends can be used anywhere B vent is used, except where it passes through walls, floors, ceilings, and inside enclosures.
On horizontal vent runs, the flue pipe must be pitched down toward the terminal end—1/4-inch per foot for condensate drainage—for the entire length of the horizontal vent run . Failure to pitch the vent run properly may damage the heater due to condensate running back into the unit .
Horizontal vents are installed along the length of a drainpipe and are typically used in homes with long, straight drainpipes. They are less expensive to install than vertical vents, but they can be more difficult to clean. Vertical vents are installed near the top of a drainpipe and extend up through the roof.
Not to exceed one-third of the total permitted length of a vent shall be permitted to be installed in a horizontal position.
Type B vents must be equipped with their own special chimney caps. If the cap is damaged or lost, it should not be substituted with something not recommended by the manufacturer. The clearance required from combustible materials is printed on the flue's exterior metal surface, and is generally 1 or 2 inches.
Type B Gas Vent requires a minimum of one-inch clearance to combustibles. This one-inch is a typical clearance for all brands of Type B Vent, but each section of vent pipe is marked with the clearance required by Underwriter Laboratories, so it should be checked.
Maintain a pitch or rise from the appliance to the vent cap on horizontal runs. The pitch shall not be less than ¼ inch to the foot.
Vent pipes must be installed so they stay dry. This means that they should emerge from the top of the drainpipe, either straight vertically or at no less than a 45-degree angle from horizontal, so that water cannot back up into them.
If you have 1 ¼-inch pipe, the horizontal distance of the vent should not be more than 30 inches. For a 1 ½-inc pipe the vent should be 42 inches away at the most while a 2-inch pipe must have a maximum distance of 5 feet.
Appliances designed for natural draft venting and incorporating integral venting means shall be located so that a minimum clearance of 9 inches (229 mm) is maintained between vent terminals and from any openings through which combustion products enter the building.
A 1-inch clearance (air space) to combustible materials must be maintained, when using DuraVent Round B-Vent, regardless of the pipe diameter. at least 2 feet higher than an adjacent wall or obstruction, if it is within 8 feet.
A plumbing vent does not necessarily have to go straight up. While it is common for vents to run vertically and extend through the roof, there are alternative venting methods available, including: Horizontal vents: These vents run parallel to the building's floor and connect to a vertical vent or vent stack.
There is currently no maximum or minimum length specified in the building regs. They do say that single skin flue pipe mustn't pass through any roof space, floor or internal wall.
Selkirk Type B Gas Vents 3 through 24 inch sizes must be installed with ONE INCH MINIMUM AIR SPACE CLEARANCE TO COMBUSTIBLES! 26 through 48 inch sizes require TWO INCHES MINIMUM AIR SPACE CLEARANCE TO COMBUSTIBLES. These clearances are marked on all gas carrying items.
Type B Gas Vent has been engineered to heat up rapidly. It remains hot during the operation of the appliance with minimal condensation in the appliance and vent system.
Don't confuse AAVs with smaller and cheaper mechanical vents. Sometimes called "cheaters," these tubular, spring-loaded $5 vents are rated for only 1/2 DFU (drainage fixture unit), and are not allowed under most building codes.
Type B gas vents may be used to vent gas appliances listed for use with Type B gas vent. Hart & Cooley Type B vents are not to be used with appliances burning solid or liquid fuels.
Direct vent is much more efficient, you're pulling fresh air from outside of the house. While you're simultaneously exhausting and gives you more flexibility from an install stand point and most of all direct vent systems are going to heat much better because they are sealed units.
For example, a 6-inch (152 mm) diameter Type B vent must extend above a simple gabled roof only 1 foot (305 mm) for roofs having up to 6/12 pitch, if the terminal is not within 8 feet (2438 mm) of a vertical surface such as an upper-story exterior wall.
It's typically recommended that you go with a 2" PVC pipe for the vent. This is according to the uniform plumbing code (UPC). It may not be enough, depending on how many fixtures you are trying to run off the vent. You should check with local building code requirements to be on the safe side.
No more than four water closets or bathroom groups shall be installed on a 3" horizontal fixture branch. EXCEPTION: Where the water closets are rated 3.5 gallons or more per flush, no more than two water closets or bathroom groups shall be permitted.