Can't get rid of the smell of gas sewerage leak, under my kitchen sink.

[RedDragon]

There is no smell coming out of my sink plughole, never has been.
There are no water leaks in the piping and U-bend under my sink.
Have tried on several occasions using very strong drain un-blocker and odour remover, to remove smell, but has not worked.
Sink plughole never blocks up and water runs freely and quickly through plughole.
Sewerage gas smell, seems to come from both threads/nuts at both ends of U-bend and the thread/nut where it joins the waste pipe and finally another thread/nut on the waste pipe, where the pipe disappears through kitchen cupboard and into the cavity wall.
I live in a first floor flat, above me is another flat, with the kitchen directly above me.
Below me is the ground floor and I'm directly above their bathroom/toilet.
The main waste pipe is in the cavity wall behind my kitchen cabinet, which runs from upstairs down to the ground floor and joins the sewer I presume.
The upstairs flat experience no smell in their kitchen or bathroom whatsoever.
Plus the downstairs flat also experience no smell in their bathroom/toilet and kitchen.
This has been going on constantly all this year and sometimes despite the kitchen cupboard under the sink, with the door firmly closed the smell of sewerage is over-powering.
Hope you can kindly advise me what to do.
I'm on low income, an old age pensioner and rent my flat privately.
Unfortunately landlord simply suggested that I try using baking powder and white vinegar to remove smell.
So far this has been unsuccessfully.
What would you advise me to tell my landlord how to fix it himself.
As I feel he is reluctant to use the services of a professional plumber.
I look forward to everyone's reply.
Thank you kindly in advance for all your help and support now.

 

[gpbeck]

It would help to see a photo of under your sink.

 

[RedDragon]

Hi gpbeck,
Thanks for your suggestion.....have now attached 2 photos, of all plumbing under my sink.
Further information, never had a problem in all of 13 years, with the same plumbing, until this year.
Never use the washing machine, as a friend does all my laundry.
However to see if I could fix my problem. I ran the washng machine last week. Next day, there was a NEW foul smell (and not coming from under my kitchen sink, but around and underneath my washing machine) but not of leaking sewerage gas. Landlord's workmen, promptly arrived, discovered that the waste pipe on my washing machine must have come loose after I did the ONE wash. They duly fixed it and immeadiately "the NEW foul smell" disappeared and fortunately has not returned.
Still persevering each day, using baking soda and white vinegar down plug hole and leaving, then rinsing with hot water, but still no improvement with the constant smell of sewerage gas, under my kitchen sink and in the cupboard.
Just to reiterate, I have had this smell of sewerage gas, underneath my kitchen, consistently for 6 months.
Further information, my landlord owns his own building company (20 years)

and built my block of flats and many, many more houses, etc. So I presume he must know a lot about everything involved in the whole plumbing process of a building, etc.
Hope the photos are of assistance now.

 

[gpbeck]

The basic layout looks ok. I don’t think vinegar etc will ever do anything if there is a significant blockage. I think good start would be to disassemble the white pipes (white collars should only be hand tight), see if they need cleaning internally as may have sludged up. U bend will have contents so put basin beneath.

 

[RedDragon]

Hi gpbeck,
Thanks for your reply. The workmen have already disassembled the white pipes, said they were ok. But agreed strong bad smell coming from waste pipe. Then they assembled again and just left, saying they would report back to landlord. The landlord did try to blind me with science, after they fixed my washing machine and said re underneath my sink "that there was an air bubble and it was all to do with the pressure of water and would all be ok in a couple of days"
His workmen, disassembled the white pipes, the day after, what the landlord told me.
His wife who helps run his business and takes the majority of enquires, messages, etc.....said she would look for solution on the internet.....hence getting back to me about baking soda/vinegar......am really at a loss and quite exasperated unfortunately....wondering where I go from here?

 

[gpbeck]

If all those white drain pipes are clean and assembled correctly they will be sealed, water and odour proof. The smell is therefore probably coming from behind or under the unit but not those pipes.

 

[Stigster]

The bottom line is that under normal pressures encountered within waste pipes and fittings, they are essentially gas tight. If you can smell gasses they are also normally leaking water during use. You would surely notice water escapes no matter how small during your investigations. It's not impossible for gasses to leak where water cannot but it's highly unlikely.

I can only suggest replacing all the rubber seals in the fittings, just in case, and seeing if the smell persists. In the absence of fresh seals I would disassemble and wrap all seals with a couple of wraps of PTFE tape. That's a bit of a bodge in place of new seals but sometimes needs must.

Just to be absolutely clear, the smell is coming through the pipework and definitely not out through the waste inlets/plugholes?

I would be starting to suspect another source for the smell. More than once I have found an open end or a boss connection unused and without a cap or plug. Sometimes in hidden places.

It might be worth getting a camera probe with built in light behind those units to see what's up. Some plumbers carry them and they are surprisingly cheap nowadays if you need to buy one.

 

[Aquarius]

Personally I think your smell could be stagnant water coming from that massive loop in your overflow pipe (black corrugated pipe). However that would normally be a smell in the kitchen sink area as opposed to under it. Could be smell from behind cupboards as suggested.