Every month the washing machine will start not draining so we have to unblock the pipe. Every month yellow greasy clumps come out and we do not know what it is. I don’t use powder I use gel and have tried different ones. So I don’t think it’s the washing stuff I use.
This is something to do with defects in the drainage pipe layout. I bet you have a dishwasher as well as the sink connected to the same outlet. The greasy clumps are mini fatbergs which form because the waste doesn't drain properly. Definitely not anything to do with washing stuff.