I have just moved into my house. There are terrible smells eminating into it seems 3 rooms all containing plumbing. I understand a little about traps and soil stacks. So a plumber is looking into replacing traps on my bath and shower as there are smells coming from there too but there is a really bad smell coming into the Utility Room downstairs. In there, there is a sink (which I am told the pipes are clean), washing machine and it seems the internal soil stack (of which I cannot locate the end to check if there is an AAV attached or AAV problem)...It is not in the loft and there is no evidence of it in the house anywhere. I have two bathrooms which back onto each other, one of which is above the utility room. Where do i start to at least minimise disruption? A plumber told me that there also seems to be a 3" pipe behind the sink in the utility room which we don't know what it is connected to as behind a load of units (which he said was strange as this is usually a rain type pipe) . This house seems to have everything boxed in and loads of plumbing? Can anyone give me any guidance, are there any checks I can do - its driving me crazy..... I also have no external access to have the pipes jet cleaned....