Double Sealed Manhole within new extension

Discussion in 'Builders' Talk' started by HERSHAM BOY, Sep 11, 2018.


    HERSHAM BOY New Member

    I am in the process of digging out footings for a double storey side extension. There is an existing manhole in my side driveway which my neighbours foul waste passes through and on into my other neighbours property.

    I had intended to install a double sealed manhole and tile it into the floor of my new utility room. My builder contacted Thames Water who advised him that the manhole must be relocated outside the property a minimum of 200mm from the boundary and 500mm from any new walls. Add to this the 450mm or so for the actual manhole and I have lost almost half of my proposed 2100mm extension.

    Please see the attached plans.

    Any thoughts or experiences gratefully received.

    Attached Files:

  2. Isitreally

    Isitreally Well-Known Member

    Whether or not you lose your extension you need to clean all the carp out of it before you end up with a major blockage causing your neighbours problems they don't deserve.
    KIAB likes this.
  3. KIAB

    KIAB Well-Known Member

    If you can locate a manhole outside of a extension,do so, nothing worse than a manhole inside a house, & even worse with raw sewage flowing through the ground floor, if it blocks.

    As above clear the carp out, asking for serious problems.

    Manhole ain't that deep, so difficult to locate further away from property as lack of gradient for pipe.
  4. sospan

    sospan Well-Known Member

    The Water companies are getting a lot more strict on building near any shared sewer pipes. The problem you have as well is the waste from your downstairs toilet and also from the new utility room are all going to converge at the same point and its going to be impractical to reroute the pipes away from the property.

    The only thing I can think of that may help is to fit a rodding point outside the building. That way, if it does block the man hole could be jetted without lifting the internal lid
  5. stevie22

    stevie22 Active Member

    Who did your design? This was a problem from the getgo.

    Have you for full plans? BC should have picked this u prior to approval.

    Be grateful you've got Thames: Anglian are much less helpful

    HERSHAM BOY New Member

    Just to follow up on this. We do have a conclusion.

    Thames water (I believe all other water boards also) no longer allow a double sealed manhole cover within the property if it is classified as a public sewer i.e shared with a neighbour.

    I had to purchase a buildover agreement which had a 21 day lead time at a cost of £299. As I was keen to progress with the build I blagged that I was concerned about the exposed pipe and they put me on the Jeopardy list which had a 24 hour turnover.

    Conditions were as follows:

    1. Manhole to be located outside 100mm from any walls in all directions

    2. Existing clay pipe must be replaced with like for like.

    3. Chamber to be constructed of concrete or engineering brick.

    Job done.

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