Unable to find the top of my soil stack

what do you plan on doing when you find the top of the stack ? blow down it ? :-) If you're soil stack is boxed in and you don't see it in the attic its possible it may have a Air Admittance Valve inside the boxing An air admittance valve allows air to be pulled but doesn't let smell back out of the top, sort of like a one way valve. also you say the only pipes you see at the top are vented ? well the only pipe which should be vented at high level is the soil stack - soil&vent However, finding the top of it isn't going to solve you're problem. If everything is getting blocked then you may need you're drains flushing. you may need a company such as Dyno. good luck

Your stack is probably in a tight corner of the loft under some rockwall. Its definetly got an air admittance valve on or you would know it was up there. You can't unblock the stack from the top any way. Try having your drains rod through and see if that works first. Good luck