sewer smell from vents when AC or furnace go on

[undecidedcoin]

Hello,

There is a faint wiff of sewer smell when the AC or furnace goes on. All of my research suggests it's an issue with the condensate drain line. I've attached photos of what it looks like. Is there no P trap and hence sewer gas smell is being sucked into the vents somehow?

 

[Plumber69]

Hello,

There is a faint wiff of sewer smell when the AC or furnace goes on. All of my research suggests it's an issue with the condensate drain line. I've attached photos of what it looks like. Is there no P trap and hence sewer gas smell is being sucked into the vents somehow?

Maybe one of your ptraps are dry or a floor drain

 

[Sponsor]

 

[undecidedcoin]

hi plumber69 thanks for the response. there is no floor drain in the basement so the condensate line just drain into a pump. how would the dry floor drain end up getting into the vents? are you assuming the condensate drain went into the floor drain and it "syphons" the smell somehow?

 

[Jadnashua]

Condensate drains do need a p-trap, but, that will often evaporate in the winter once the a/c is turned off. If your duct supply/return isn't balanced and is leaking, it can suck air from any location it can, and that might be from an open connection to the sewer (one without a trap).