(Photo: Hugh Cairns)

This high efficiency furnace was installed in a brand new home. Broken or improperly installed vented pipes can have serious consequences if they leak toxic gases into the home.

Just like their predecessors, new high efficiency furnaces burn natural gas. While creating heat, they also create carbon dioxide and carbon monoxide gases. Both these gases are toxic in high quantities with carbon monoxide being very toxic. High efficiency furnaces operate with a vent motor that pushes combustion gases through a vent pipe directly outdoors. The vent pipe creates a positive vent static pressure and it must be airtight so the products of combustion will not leak out of the vent.

The temperature of the expelled gases is low. That means the gases can be vented using special plastic PVC pipe. Because plastic pipes can be used there is no need for a chimney. No chimney means reduced costs in new home construction.

When the furnace is operating it produces condensation. Proper vent piping installations will have the piping gently sloped back toward the furnace. This will allow for the condensate to drain back to the condensate pump. This also keeps ice build-up from forming on the discharge pipe outside – the danger here is that the vent pipe gets completely blocked.

Because high efficiency furnace venting systems must be air tight, PVC vent pipe connections should be monitored periodically during furnace operation for any moisture / condensation or gas spillage. If such occurs on PVC joints, you should have this condition evaluated by a licensed HVAC contractor, the connection will have to be resealed.