I bought an old farm house that has a septic system. The bathrooms all run into the septic tank but the kitchen sink, dishwasher and clothes washer run into a separate tank. I am not sure if it is a tank or an old septic pit of some kind. This second gray water system does not have a vent so I occasionally get sewer odor coming from the clothes washer drain where the hose goes into the pvc pipe. This clothes washer does not have a trap but there is a u-bend in the drain hose. I plan on adding a trap to the 1 1/2 inch clothes washer drain and an AAV valve. Can I also put in a vent on the outside of the house where the dain line goes into the ground/pit?
The line starts at the sink/dishwasher then goes 13' to the clothes washer then 6' to the outside wall then down into the ground. I have attached 3 photos. One of the washer drain, the other is the outside wall where the drain comes out and goes into the ground and the 3rd is a larger view of the outside wall where I want to run a vent pipe up.