Hi, I have recently removed the broken dishwasher we inherited with our new house. The waste pipe for the dishwasher was connected to the same waste pipe for the washing machine. Now the dishwasher and its waste pipe have been removed it has left a open gap (see picture). Due to the waste pipe for the washing machine being inserted above I need to block off the gap below. What is the best (and quickest) way of doing this? Can i get some sort of a plug/stopper to put in it?