Installation Rules for Flue Pipes
(also called stove pipe, smoke pipe, chimney connector, etc.)
The rules provided here are based on the CSA installation code used in Canada. For the exact rules in your area, check with a local wood heat retailer, chimney sweep or building inspector.
- Maximum overall length of straight pipe: 3 m (10 ft.)
- The assembly should be as short and direct as possible between the stove and chimney. The use of two 45 degree elbows is often preferable to a single 90 degree elbow because less turbulence is created in the exhaust flow and they result in less horizontal run.
- Maximum number of 90-degree elbows: 2. Maximum unsupported horizontal length: 1 m (3 feet).
- Galvanized flue pipes must not be used because the coatings vaporize at high temperatures and release dangerous gases. Use black painted flue pipes.
- 6-, 7-, and 8-inch diameter flue pipes must be at least 24 gauge in thickness.
- Flue pipe joints should overlap 30 mm (1 1/4 in.)
- Each joint in the assembly must be fastened with at least three screws.
- The assembly must have allowance for expansion: elbows in assemblies allow for expansion; straight assemblies should include an inspection wrap with one end unfastened, or a telescopic section.
- Minimum upward slope towards the chimney: 20 mm/m (1/4 in/ft.).
- One end of the assembly must be securely fastened to the flue collar with 3 sheet metal screws and the other end securely fastened to the chimney.
- There must be provision for cleaning of the pipes, either through a clean out or by removal of the pipe assembly. Removal of the assembly should not require that the stove be moved.
- The crimped ends (male) of the sections must be oriented towards the appliance so that falling dust and condensation stay inside the pipe.
- A flue pipe must never pass through a combustible floor or ceiling or through an attic, roof space, closet or concealed space.
- Minimum clearance from combustible material: 450 mm (18 in.). The minimum clearance may be reduced by 50 percent to 225 mm (9 in.) if suitable shielding is installed either on the pipe or on the combustible surface.
The ideal flue pipe assembly is one that rises straight up from the appliance flue collar and directly into the chimney with no elbows. The system at the right is single wall pipe with an inspection wrap (pipe coupler) to allow it to be assembled and disassembled without moving the stove.
A straight flue pipe assembly offers the least restriction to gas flow and results in stronger draft. Straight assemblies also need less maintenance because there are no corners for creosote deposits to accumulate.
A perfectly straight flue pipe assembly is another good reason to install chimneys up through the warm space of the house, instead of out and up and outside wall.
Certified double-wall flue pipe systems are also available. These systems are tested to determine the minimum clearance at which they can be installed. The clearance information is found on the labels attached to the pipe and in the manufacturer's installation instructions. The rules for their installation may differ from the rules for single-wall flue pipes.
The minimum installation clearances for certified double-wall flue pipes are much less than those for single-wall pipes. Also, the maximum length of a double-wall flue pipe assembly may be greater than is permitted for a single-wall pipe.
There are two general types of double-wall flue pipes: sealed and vented. A sealed double-wall flue pipe is effective at retaining the heat in the flue gases because the air space between the inner liner and outer shell acts as an insulator.
A sealed double-wall pipe is a good choice to maximize draft and minimize creosote deposits. Use sealed double-wall pipes if the assembly must be long or if the appliance is expected to produce low flue gas temperatures. The system to the left uses a sealed double wall telescopic length between the stove and chimney.
A vented double-wall pipe allows cooling air to pass between the inner and outer layers. Where the flue pipe assembly is short and straight, a vented double-wall pipe can be acceptable. However, vented pipe is not a good choice for longer flue pipe assemblies or for appliances that are expected to produce low flue gas temperatures.