Help with a sewage odour beneath extension / kitchen

Discussion in 'Getting Started FAQ' started by 319Mike, Oct 4, 2018.

  1. 319Mike

    319Mike New Member

    Right, so here goes

    I recently purchased a 1930's semi which has a gable and rear extension.

    Problem: I am experiencing an odour entering the property through intricate gaps in the under stairs cupboard and floor void in the kitchen - mainly in the area where the soil stack runs down through the cavity wall and meets the kitchen floor (where the old inaccessible manhole is beneath the tiled floor)

    Resolution: let the process of elimination commence.........

    I've sealed all visual gaps where the odour was clearly coming through with expanding foam and it has alleviated the odour greatly but I'm not comfortable knowing that all I've done is put a plaster on the problem. Every now and then especially when high winds occur and at certain times of day mainly between 19:00 - 21:00 (Pattern) the odour returns (faint lingering whiff of methane, possible sewer gas and smells like musky farts - sorry for the detail but it's true and very unpleasant!

    Initially thought it could be gas but so had the gas systems checked by BG, no gas detected and gas meter/boiler in perfect working order - haven't checked gas fire in the living room yet but he did advise if it was gas it would have registered on his meter and smelled more like a dead rat than gas!.

    Next I had a CCTV survey done on the main sewers to ensure there were no blockages/damaged drains and these are all in very good condition with no issues and the sewer flow is excellent.

    What the CCTV has pin pointed is a possible redundant blind connection at 0.19m from the man hole/main foul sewer outside the property where it enters the property from the main manhole going into the extension - We flushed the toilets/ran all the facilities and nothing came out so we believe this to be redundant and a possible ingress point from main foul sewer into the property. What the issue is that the CCTV camera could get into this to see where it leads and I'm struggling to understand what this pipe is, where it goes and what it may connect to!!! driving me crazy.

    Next step will be to check the stack vent on the roof for blockages which I hope to have done very soon and then if that proves ok I'm looking at possible excavation to check the main drain traps. However these are all looking fine with clean water in the trap, no blockages and have flushed / visually inspected flows so reluctant to carry out any demolition/inspection works here.

    I've drawn up a diagram of the drainage system for the property and the schematic from the CCTV survey which shows the 3 manholes/foul sewer pipes and where the blind connection is at 0.19m (small arrow) I really need to try and find out what this blind connection is and where it goes as I have a feeling it may lead to an old dried out gulley or is open ended and is the point of ingress - unfortunately the CCTV camera couldn't access as it was at a right angle from the main pipe - so much for no job too big!!!

    Any help and assistance or insight would be gravely appreciated from me, my fiancé and our little one :)

  2. 319Mike

    319Mike New Member

    DIAG.png CCTVSCHEM.png
    KIAB likes this.
  3. KIAB

    KIAB Well-Known Member

    Redundant blind connector is it going towards another house,or inspection chamber or a dead end.
  4. Richard_

    Richard_ Active Member

    It's not much help to you but when I started design any notion of hidden intenal stacks or downpipes was swiftly beaten out of us. On a large commercial project you can be sure there will be a blocked pipe every few years and if you can't get to them then you'll have a problem.

    So, is there any access to your internal stack? Is it boxed with plasterboard so you could cut an inspection hole (in the board not the pipe) to see if the outside of the pipe is wet from a leaking joint above. Obviously best if this can be done at the bottom of the stack.

    It may take a few flushes of each toilet, sink, shower and bath to get the leak to run down the pipe.

    The smell of the air in the hatch would quickly reveal if you'd found the problem!

    Perhaps someone could get on the roof and put a camera down to check it is OK, although a leaking joint wouldn't show on an internal camera.

    Final thought, is the original house a suspended timber floor? If so the location of the smell is irrelevant, you'll be smelling where it is coming through the floor rather than where the pipe is leaking.

    I presume the extension is a concrete floor from your description of the tiles over the manhole?
  5. Jord86

    Jord86 Well-Known Member

    Though I can see the house is three storeys, is it detached or does it join on to next door as a semi, any others close by? Because if the pattern of smells is mainly between 7-9pm which happens to be most families prime time for actually being in their house and using their toilet, then I would wonder if the blind redundant connection isn't actually redundant.
    KIAB likes this.
  6. KIAB

    KIAB Well-Known Member

    Thinking the same,might be the time to go putting some drain dye down the surrounding manholes,like nearest neighbours, don't use just one colour,can get confusing,by using several colours you then know from where each manhole the colour has come from.
  7. 319Mike

    319Mike New Member

    Hi All. thanks for your responses and thoughts, much appreciated

    Hi Richard, thank you for your thoughts and suggestions. I'm of the same thought that where the odour is coming from doesn't necessarily pinpoint the problem area but I'm thinking monkey see monkey do at the moment until I'm confident that my only option is to cut away at walls or dig etc...

    For piece of mind and confidence I've had the CCTV drain guys back this morning to film the blind connection whilst opening up/running/flushing all water utilities in my property and I'm 100% it's not an outlet for anything within my property.

    Problem is I don't know where this pipe leads and finding it difficult to find a company with the equipment which can navigate a camera into it as it's at 10 o'clock and naturally slightly above the level of the main foul sewer, (see attached). it's 19cm into the MH2 entry, surely there's someone out there that has the equipment to get a camera into it!!?

    I've been advised to bung the pipe - thoughts??

    Jord86/KIAB, thanks and appreciate your thoughts but I'm confident it's not outlet for an adjoining property. We are a semi detached (end house) with 3 adjoining properties. The main foul sewer serving the 4 properties runs across the back beneath the extensions as shown in the diagram. MH4 being the adjoining neighbour, MH3 being mine then out to MH2 - MH1 which are the external manholes in the side access to my property out to the road. I can see their stack that comes down exactly the same route on the property as mine which is through the extension and direct into their manhole @MH4

    Attached Files:

  8. KIAB

    KIAB Well-Known Member

    Bung the pipe, bad idea, might cause more problems than it solves.

Share This Page