Sewer smell in home

Mitch1998

Hello,
I posted a previous thread about this - but I’ve still not got the bottom of it and looking for some more help.
I have smell which ONLY occurs in my living room. It is never present in any other room. The living room is at the front of the house and is direct onto the pavement.
To the left of the front room is the alley way (for access to the rear of the property), and the communal drain runs under this. 

The smell can only be explained as rotten cabbage and I am 99% sure it smells like sewerage! The smell comes and goes - can last for days, a few hours, or isn’t present at all. We think it starts on an evening? 

I have called Yorkshire Water TWICE and both times they have checked the communal drain in the alley way, which leads to the main sewer. They haven’t identified any problems.
My partner is a plumber and cannot find any problems with the internal plumbing in the property.
I have had a builder come to check for damp/mould - no signs of either.
We have have taken skirting boards off, casing under radiators etc to check for dead rodents - nothing found. Pest control also came out but said they didn’t think it was anything dead. 

I contacted environmental health - but they were not interested.

I do live near a bacon factory - which can cause a smell down the street depending on which way the wind blows. 

HOWEVER - my neighbours have NEVER experienced this smell in their homes. I am in a mid-terrace and both neighbours have been round when the living room has been smelly and they have not had the smell before. I have spoken to people who have lived on the street 20+ years and again, they have never heard of this problem. 
Please help - I am at my wits end, and don’t know what to do/who to ask next!!! At its worst, it’s unbearable and we do not sit in the living room. 

I am just DESPERATE to get to the bottom of the cause and get it sorted so I can enjoy my little home. 

Doozergirl

Is anyone putting out rat poison?  

Mitch1998

Doozergirl said:

Is anyone putting out rat poison?  

I haven’t put any down - I’m not aware that anybody has! 

georgehere

I know the feeling - people say dead rodents ... but you know what drains smell like - if it smells like drains, it is drains.

You need to get down on the floor and find the direction/source of the smell. If you have electrical outlets, loosen them off the wall and sniff behind them (without electrocuting yourself). If your walls are dry lined or stud construction, the smell can travel behind the dry lining from other locations.

Close the door and check from both sides, laying on the floor, around and under - just in case it is actually coming from the hall.

Get a ladder and loosen the light fitting. Loosen light switch covers. Fireplace, chimney.

Do not stop until you find the direction/source location - it will be coming from somewhere. It is most likely coming up ... hence spending a lot of time laying down on the floor is worthwhile.

Once you have a clue on the direction - you can follow up and start working out which drain/drain section it is coming from.

It may take several days, it may require you trying at different times of the day/night. It is surprising how small a gap/hole/crack can pass through the smell and create a strong odour in the room. I'd like to say there is an easy answer, but there isn't. But I can tell you that if it is drains, then there is a source and you will eventually track it down.

It is also possible that the smell is coming from outside - but you will have spotted that by now - that would be a poor fitting drain cover or a vent and be very obvious.