Hello. I am planning to get a Bosch washer/dryer set that includes a ventless/condensing dryer (WTC82100US and WAE20060UC). The dryer manual says it can use the same drain as the washer if there's room, but currently I only have a single 1 1/2" standpipe. To make the room for both drain lines, do I just need to add a wye at the top, or do I have to account for potential backflow from either unit to the other? Any advice for this situation would be most welcome. Thanks.