Waste Diameter Query

Discussion in 'Plumbers' Talk' started by Vin, Jan 22, 2019.

  1. Vin

    Vin Screwfix Select

    I'm a bit bemused, I am trying to buy a fitting for my existing waste to allow me to connect a shower.

    I assumed the waste pipe in my house was 110 mm but thought I'd better check and it seems to be approx 113 mm outside diameter.

    Does the 110 mm refer to the inside diameter or have I got some old imperial stuff in my house?

    The house was built in 1968 by the way.

    Thanks
     
  2. KIAB

    KIAB Super Member

    If soil pipe is plastic, then it will be 110mm external diameter, can use a strap on connector with a 40mm boss to connect pipe from shower.
     
  3. Vin

    Vin Screwfix Select

    Unfortunately there is no room to fit a strap on boss so I was going to replace an existing 92.5 branch with a new one that has a boss connector like this https://www.screwfix.com/p/floplast-sp190-92-5-branch-black-110mm/29610

    I'm not sure it will fit though, I am a bit surprised my existing pipe is such an odd size!
     
  4. Vin

    Vin Screwfix Select

    Perhaps I have measured it wrong, I can't directly measure the diameter so I measured the circumference and worked it out from that
     
  5. KIAB

    KIAB Super Member

    If soil pipe is plastic, then it will fit.
    And if soil pipe terminates through roof, be careful if you need to push soil pipe up, as you will most likely dislodge the weather slate.
     
  6. WillyEckerslike

    WillyEckerslike Screwfix Select

    The Teach likes this.
  7. There are some makes that are not compatable with each other.
     
  8. Vin

    Vin Screwfix Select

    I have just had a close look at one of the fittings and it says 4" 112mm on it.

    Does this mean 110 fittings will not work or will they be ok?
     
  9. Vin

    Vin Screwfix Select

  10. KIAB

    KIAB Super Member

    Waste pipe 32mm/40mm incompatibility between brands,but in nearly 40 years I have never seen it with 110mm plastic, maybe just lucky.
     
  11. KIAB

    KIAB Super Member

    Got a make on it.:confused:
     
  12. KIAB

    KIAB Super Member

    Acess might be tight,if can't even get a strap on boss fitted.

    [​IMG]
     
  13. ecoplumbing

    ecoplumbing Active Member

    Is the soil pipe internal? You'd probably be ok using the new 4inch fittings but if it is internal then it can be a real pain to fit- limited space to cut the pipe, then you'll need to chamfer the edge otherwise you'll struggle to get the new fittings on. I'd really try and find a way to use a stap boss if it's possible
     
    KIAB likes this.
  14. longboat

    longboat Screwfix Select

    Fittings are denoted by their internal diameter so 112mm should be about right to fit onto a 110mm pipe with a slight clearance for the rubber seal.
    When you measured the circumference of the pipe you should take the thickness of whatever you used (string, tailors tape, etc)
    Into account as the outside diameter will be slightly bigger than the internal.
    If you calculated 113, then I'm sure the true measurement will be 110.
     
  15. The Teach

    The Teach Screwfix Select

    The fitting below can be attached to your existing branch,Dismantling vintage soil plastic plumbing and getting new to fit/seal is a ballockache

     
  16. Vin

    Vin Screwfix Select

    I will have another look tomorrow but the soil pipe is internal and the only place I can accesss it and get a fall is right in the middle of the existing branch. I have found a supplier online who sell imperial fittings so that might be another option.
     
  17. Vin

    Vin Screwfix Select

    You might have something here!
    I measured the circumference using a bit of wire but didn’t take into account the thickness of the wire!
     
  18. Vin

    Vin Screwfix Select

    A quick update!

    I managed to use a McAlpine mechanical boss but I had to drill the existing branch.

    It worked really well though and doesn’t leak so thanks for all the help, the mechanical boss is well made and easy to use...highly recommended!
     
    longboat and WillyEckerslike like this.
  19. ecoplumbing

    ecoplumbing Active Member

    Good old mcalpine. Best waste fittings around in my opinion
     
    Vin likes this.
  20. Vin

    Vin Screwfix Select

    I agree they are good, I used a McAlpine waste for the shower as well, quite expensive but probably worth it .
     
    ecoplumbing likes this.

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