Hi, My first post here. So builder has finished his work but I think a trap is missing from the wash basin and the washing machine waste. Which explains the smells that come every now and then. I'm thinking I could add an inline osma siphon to each or one shared between the two. Or an s trap shared. I've attached a photo. From the right side the pipe coming in is from the wash basin which has no trap. Any pointers? Or best to call a plumber.