Plumbing

Smelly downstairs WC issue?

Anonymous user 09/03/2024 - 3.20 PM

I recently bought a 3 storey town house which is only 4 years old. Since day 1 we have been having sewage smell in our ground floor wc. It gets especially worse when one of the toilets on the floor above is flushed after a dump. No other toilets are impacted (have 4 in total). Called in a plumber previously to make sure that the smell was not due to a broken seal behind the toilet. He opened the toilet up and could feel a lot of air being pushed through the soil stack. He suggested that it might be a faulty vent. I got in the loft found that the stack pipe was not connected to a roof vent instead had an AAV installed. Took off the AAV as reviews online said it was not a good a quality one and tends to break quickly. I intended to change the AAV with a better quality one but didn't get around doing it immediately. For a week the stack pipe was left open in the loft and the smell in the wc vanished. Got a new AAV and installed hoping this will resolve the smell once and for all however the day after I installed a new AAV the smell came back in the wc. Did some research online and decided to join the stack to a spare roof vent (had 2 in the roof) using a flexible ducting pipe. Tried that but the smell remains. The smell tends to remain early morning or when the top floors toilets are flushed. It tends to vanish otherwise. Had another plumber come in and check the drains with cctv. He suggested it might be the sink. He cleaned the sink assembly and made sure all seals were properly installed but the smell still remains. Not sure what exactly is the issue. Has anyone else experienced something similar? How can it be resolved?