The washing machine is currently discharging into a line that is not trapped and is also too small for the fixtures using it. The line is currently serving the bathroom sink as well as the washing machine. In order to properly connect the washing machine, The fixture drain will have to be upsized to 2 inch pipe. The fixture drain is currently 1 1/2 inch pipe and there is no trap serving the washing machine. A p trap with a standpipe will also have to be installed for the washer to discharge into.