gurgle in furnace condensate line

[John Dirks Jr]

While inspecting a direct vent HE furnace today, there was a gurgling sound coming from the air gap at the condensate discharge line.

I went outside and and checked the vent and intake pipes. It felt like there was way more exhaust being blown out the discharge than air being sucked into the intake.

What is happening here? I've never heard the condensate line gurgle like that. I assume that the draft fan is pulling air in through the condensate line. If so, why would this happen and what are the implications of it?

[shadow67550]

If the furnace has just been started there may not be enough condensate built up in the furnace condensate trap to be effective. Pour some water into the trap and it should stop. the Manufacturers recommend this when we start up a furnace.

Possible the trap has a crack in it that allows the water to seep out and again cause an ineffective trap for the condensate . The combustion vent blower pulls a negative pressure on the trap so there is little chance of flue gasses excaping. It can throw off the gas air mix to the burners however.

[Jim Katen]

If the furnace has just been started there may not be enough condensate built up in the furnace condensate trap to be effective. Pour some water into the trap and it should stop. the Manufacturers recommend this when we start up a furnace.

Possible the trap has a crack in it that allows the water to seep out and again cause an ineffective trap for the condensate . The combustion vent blower pulls a negative pressure on the trap so there is little chance of flue gasses excaping. It can throw off the gas air mix to the burners however.

Or it could be a cheezy running trap without enough depth.