I have a shower on the first floor that does not have a P-trap. A previous owner did some remodeling and the shower drain pipe is plumbed right into the top of the waste line with a tee. You can see the connection just behind the supply lines at the back of this picture: The flow is from the back left of the picture to the front right. The tee closest to the camera is from the toilet. The piping runs a few feet further and then joins the soil stack.
What are my options for adding a proper P-trap here? can I put a pair of 45 degree fittings to jog the shower pipe around the waste line, add the P-trap and then rejoin the waste line from the side instead of the top? Is there some other approach?
This is all above the ceiling in a finished basement so I know I will have some drywall work to do no matter what.