[Stock Punk]

When the basement sump pump runs the drains in my kitchen gurgle loudly.
The sump pump well is in the basement and is the discharge for the CWM.
The pump also discharges water.
The discharge pipe connects to the main sewer line to the septic tank.
The kitchen is on the first floor one room away from where the pump and CWM are.
The kitchen sink is a double sink. Each drain empties with its own trap and then meets under the sink to the common drain. The common drain from the sink connects to the drain line from the sump pump then both are common to the main sewer line out.
Under the sink where the two drains connect together is an air valve (this was put in years ago by a plumber because when both sinks were full of water the draining was very slow).

Connecting to the main sewer out is the 2nd floor bathroom. The sink, tub and toilet in this bathroom do not have any draining, flushing, or gurgling issues; the gurgling is only with the kitchen sink drains.

Years ago I had bubbling coming up from the 2nd floor toilet. We found the air stack blocked and pour a chemical down it at the recommendation of a local hardware store (now closed). That solved that issue. I could actually hear the blockage clear out making a loud draining sound.

Because I don't have gurgling or bubbling in the upstairs bathroom drains and toilet, I don't think the main stack is the problem. The sump pump and kitchen both connect to the main sewer line that the upstairs bathroom connects to so they share the same stack.

I suspect the air valve under the sink. But I am not experienced in plumbing beyond replacing sump pumps. The fixtures under the sink are PVC and looked cemented.

Any advice?