Directive: Plastic BH Venting Systems

This directive is being issued by a provincial safety manager pursuant to section 30 of the Safety Standards Act.

 

Scope

This directive clarifies requirements for plastic BH (special) gas venting systems based on strategies applied by other authorities having jurisdiction across North America.

 

Details

CSA B149.1 - Natural Gas and Propane Installation Code requires plastic venting to be certified to ULC S636, the Standard for Type BH Gas Venting Systems.  

The ULC S636 standard requirement was put in place due to a number of plastic gas venting system failures identified with ABS plastic pipe and fittings. Investigated failures involved stress cracking and melting. Such failures in a dwelling unit could expose occupants to carbon monoxide that results in personal injury.  

Existing gas appliances with plastic venting systems operating in a safe compliant manner do not require action until replacement of the associated appliance takes place.  

BH special gas venting systems must be selected and installed based on the appliance and venting manufacturers certified installation instructions.

Gas Appliance Replacement

This section applies to plastic venting systems installed prior to recognizing the ULC S636 Standard for Type BH Gas Venting Systems.

When replacement of the entire plastic venting system is not possible, or impractical due to specifics of a particular installation, the gas installation permit holder may use the existing plastic venting system provided that all the following conditions are met.

1. It is not possible to replace the entire plastic venting system.
2. The first five feet immediately downstream of the appliance is replaced with venting that is:  
   • suitable for the appliance; and,  
   • certified to ULC S636.  
3. An accessible existing plastic venting system is visually inspected and found to be in a good, safe working order. If the venting system displays cracking or any damage the complete system must be replaced.  
4. The complete existing plastic venting system is pressure tested in accordance with the following.  
   • The test gas used must be air or an inert gas.  
   • A minimum test pressure of positive or negative seven inches water column shall be applied to the entire existing plastic venting system. Test pressure shall not exceed a pressure of 2 psig at any time.
   • The minimum test pressure of +/- 7 inches water column shall be measured by either a pressure gauge or equivalent device and, if a gauge is used, the minimum diameter shall be 3 in (75 mm) and the maximum range shall exceed the test pressure by at least 15% but not more than 300%. The pressure gauge or equivalent device shall be calibrated to read in increments of not more than 2% of the maximum dial reading of the pressure gauge.
   • The minimum test pressure shall be applied for at least 5 minutes and at least 75% of the test pressure shall be retained — if less than 75% pressure is retained, the entire plastic venting system must be replaced.
   • Where it is not possible to reach the venting termination due to elevation or other access issues, it is permissible to test up to the interior side of the outside wall piece. This will require cutting the venting at the inside of the wall-piece, testing remaining concealed interior venting and installing a S636 certified coupling to re-attach the venting to the wall-piece.

If the plastic venting system fails the pressure test, the entire system shall be replaced with venting suitable for the appliance and certified to ULC-S636.  

ABS components affixed to and shipped as part of the appliance - ABS venting components integral to the appliance are considered to be approved as part of the appliance. Venting components supplied loose or not factory attached must be ULC S636 certified components (PVC or CPVC).  

Any form of cellular core venting material will not be accepted; all existing cellular core venting material shall be replaced at the time of appliance replacement.  

Provincial Safety Manager, Gas

 

References:
Safety Standards Act
Gas Safety Regulation
CSA B149.1 - Natural gas and propane installation code
ULC S636 Standard for Type BH Venting Systems