The washing machine drain currently runs into an open plastic u-bend, through the wall to the outside and directly into the soil stack, as here... Should it have some sort of trap or something? Sometimes when the toilet is flushed upstairs, we get a bad smell blown back... can't be healthy!
Mine doesn't. I should have something like this, right? https://www.screwfix.com/p/floplast-washing-machine-trap-white-40mm/18640 At the moment the stack is sometimes venting into the house...
Hi bowen192, You've answered yourself; a washing machine trap, as you have shown, is required between the washing machine and the soil stack. Should be easy to install