I am in the middle of renovating an old home (early 60’s). It’s kind of in the middle of nowhere and so far have found no plumbers willing to help, so I’m on my own. I have attached a poor sketch and a photo from under the house. Currently there is a vertical pipe into the sink cabinet which has an S-trap. A 3.5” (ext measurement) main drain pipe from the toilet and then a short horizontal run to a vent stack in the wall between the bathroom and a closet. I need to add a washing machine into that closet, so I need to correct the s-strap in the sink and add a drain line for the washing machine that’s going into the closet. I’m assuming the easiest way to remedy the s-trap is with a T and an air admittance valve in the sink cabinet. For the washing machine drain can i just add another T to that main drain that runs to a P-trap (either in the wall or beneath the floor and then up to the washing machine? It would be a pretty steep angle because of how low i would have to place the T due to the other two T’s already there. Also the two current t’s are leaking so it looks like most of that will need to be redone if there is a better way all together. Finally if i do have to remove most of what is already there is there a good way to join that ABS main line to PVC to build it out again or should I just stick with ABS.