1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Discuss Kitchen island waste in the Plumbing Forum area at UKPlumbersForums.co.uk.

  1. youngrob

    youngrob New Member

    Im in the process of extending my home and I'm considering installing a Kitchen Island with sink and I'm concerned about waste. My extension foundation block are in and built up to current floor level - I've yet to put in the hardcore/insulation and concrete slab. My island will be 2.5m from outside wall of the new extension, where a Back inlet gully will sit and flow into the existing 100mm soil - vented stack. Would it be normal practise to leave a channel in the proposed concrete slab and simply run the sink waste through this and into the back of the new gully? I'll be using Hep20 pipe in pipe for hot and cold supply. Any advice would be grateful.

  2. JCplumb

    JCplumb Plumber

    2.5m run will be OK in 40mm but I'd advise 50mm to reduce the risk of blockages especially if it will be difficult to access after installation. It can't go uphill at any point
    • Agree Agree x 2
  3. oz-plumber

    oz-plumber Plumber

    Old school mentality:

    Run 110mm on grade and reduce the vertical to 50mm to pick up the sink.
    I would never run 40mm or 50mm on grade through a slab under any circumstances, more so on a kitchen sink
    • Like Like x 1
  4. Ben-gee

    Ben-gee Plumber Top Contributor!!

    Just put the sink against the outside wall.

    Islands with sinks are so passé darling.
    • Funny Funny x 3
  5. youngrob

    youngrob New Member

    Thanks to you both for the advice. So if I run 100mm through does that get incased in the concrete slab (of which is 150) or does it run through the hardcore do u know -sorry more of a builder question I guess. I would then have to do a direct connection to the existing near by underground 100mm pipe and omit the BIG. I picked up the attached photo from polypipe website and that's where I thought the 50mm pipe would have been an option.

  6. OffshoreGas

    OffshoreGas Active Member

    Totally agree, the extra £20 in materials is nothing compared to having to dig up your floor because you scrimped the first time.
  7. youngrob

    youngrob New Member

    Yep I agree. But i dont know where the 110mm pip should sit in the floor. I dont want to put my concrete in now until I know where it should sit. The building regs doc seems unclear.
  8. OffshoreGas

    OffshoreGas Active Member

    Best thing you can do is speak with BCO, they are generally keen to help you get it right and happy to help.
  9. youngrob

    youngrob New Member

    Yes that's a good shout. Thank you.
  10. Craig Watson

    Craig Watson Plumber GSR

    If you've got the depth then fit the 110mm into the hard-core, cover in pea gravel then concrete over.
  11. oz-plumber

    oz-plumber Plumber

    I would avoid at all costs running drainage pipes in the slab.
    Run it below the slab and connect to where you have to.

    By the way, run your hot and cold piping from an accessible point, in a separate 110 mm pipe to the kitchen island.
    That way, if there's a problem, you have 1/2 a chance of replacing it with minimal damage
    • Like Like x 1
  12. youngrob

    youngrob New Member

    Sound advice - thankyou.
  13. chris watkins

    chris watkins Plumber

    Part H seems clear to me on requirements & also check out Diagram 11 & 12

    2.23 A drain may run under a building if at least 100mm of granular or other flexible filling is provided round the pipe. On sites where excessive subsidence is possible additional flexible joints may be advisable or other solutions such as suspended drainage, particularly where the pipe is adjacent to structures or where soil conditions change in the course of the pipe run.
    Where the crown of the pipe is within 300mm of the underside of the slab, special protection should be provided (see paragraph 2.44).

    2.24 At any points where pipes are built into a structure, including an inspection chamber, manhole, footing, ground beam or wall, suitable measures should be taken to prevent damage or misalignment. This may be achieved by either:

    a. building in a length of pipe (as short as possible) with its joints as close as possible to the wall faces (within at most 150mm) and connected on each side of rocker pipes by a length of at most 600mm and flexible joints (see Diagram 7(a)); or

    b. forming an opening to give at least 50mm clearance all round the pipe and the opening masked with rigid sheet material to prevent ingress of fill or vermin. It is important that the void is also filled with a compressible sealant to prevent ingress of gas (see Diagram 7(b)).

    Personally if you can achieve something like the back inlet gully (diagram in your post) with a 50mm waste run allowing for both movement & access on the up-stand under the sink & back inlet a 3m run it will be fine.
    Last edited: Jun 30, 2019
  14. youngrob

    youngrob New Member

    That solution suggestion using the BIG would be far easier if allowed.

    Many thanks for the reply -very helpful.
  15. youngrob

    youngrob New Member

    For info; I discussed with the BCO and he agreed that a 50mm pipe channelled through concrete in Back Inlet Gully was fine.
    Thanks for all advice
    • Like Like x 1
Similar Threads - Kitchen island waste Forum Date
Washing machine waste comes up kitchen sink?! Plumbing Forum Monday at 11:12 AM
Bristan Echo kitchen mixer lever screw. Plumbing Forum Jul 9, 2019