Hi while doing a remodel i notice that my washing machine has no trap, it shares a drain line with the bathroom sink, the sink has a ptrap under the sink but there is not one for the washing machine. They both have a 1-1/2 inch pipe which is goes into a 2" with a aav then in to a 3" into the main sewer line. My questions are does the washing machine need a 2" pipe, and if not can i just put a ptrap down the line from both drains to fix the problem. I am attaching a picture of the connections and a drawing of how it is set up.. thanks. I can upload a video if it will help..