Different types of vent pipes by category
All venting pipes in this category are for gas and oil-fired boilers/water heaters/furnaces only (including steam boilers) - they are not for use with wood stoves, wood pellet stoves, coal stoves and other solid fuel appliances.
All pipes and fittings for venting flue/exhaust gases from an appliance can be divided into (3) main categories. These are:
Category I - Atmospheric/Chimney Vented, Non-Condensing Only
This category includes hot-dipped single-wall galvanized pipe and fittings for connecting non-condensing (standard efficiency) atmospheric vented appliance to a masonry chimney. Most commonly these include natural gas, propane and oil-fired standard efficiency cast iron hot water and steam boilers, furnaces and hot water heaters. Exhaust gases from atmospheric vented appliances naturally rise upwards from difference in ambient air and exhaust gas temperature, and do not have any internal or external fans or blowers which assist with expelling of the gases.
Category III - Power Vented, Condensing & Non-Condensing
Category III pipe and fittings are made from seam-welded AL29-4C stainless steel alloy which is extremely resistant to corrosion. Pipe and fittings also have an internal gasket which makes the assembly air-tight and suitable for appliances which are power-vented (have an internal blower or fan for pushing out the flue gases).
Essentially, this is a universal venting category and fits all types of appliances - condensing (high efficiency ~95%+) and non-condensing (standard efficiency ~82-84%), atmospheric/chimney and power vented. However, due to high cost, it's application is mostly limited to power vented standard efficiency (non-condensing) boilers, furnaces and water heaters.
Category IV - Power Vented, Condensing Only
These are typically polypropylene (PP) vent pipes and fittings, seam-welded, gasketed and rated for use with exhaust gases.
This category is the most widely used today due to popularity of high-efficiency (condensing), power-vented appliances.
Note: Although some equipment manufacturers may allow PVC, ABS or CPVC pipe for flue applications, we advise against doing so since these types of pipe are neither rated nor intended for hot gases and may pose health and safety risks.
