Every time my washing machine releases its water into the drain line, air escapes into our bathroom sink. The sink has a vent and seems to be plumbed properly. My drain into the septic system drops a good bit, but doesn't seem to be too steep. I was wondering if the release of the water could be siphoning the water from the sink drain. Please help.

Every time my washing machine releases its water into the drain line, air escapes into our bathroom sink. The sink has a vent and seems to be plumbed properly. My drain into the septic system drops a good bit, but doesn't seem to be too steep. I was wondering if the release of the water could be siphoning the water from the sink drain. Please help.

Sounds like you have "double trouble". A partial blockage in the drain linw that's sending a bubble of air back up the line when the discharge hits the clog. But wait! If the lavatory vent were clear then the bubble of sewer gas would go up the vent instead of venting out of the trap. So that would indicate a blocked lavatory vent as well. Both the drain and the vent needs to be snaked out. Good luck, Tom