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Discuss Loo Cold Feed and Overflow Rework / Dot Dab Drywall (Part 1) in the Plumbing Forum area at

  1. Roy_66

    Roy_66 Member

    After drywall removed:
    And after removing skirting, insulation, and dabs (Architrave cutter, chisels):

    Just wanted to post of few points on my first intended project since I've hopefully learned to solder now lead free (Many thanks for the help on that)

    Project is to rework the loo cold feed and overflow, by cutting into wall as above pics.

    Originally pipes were routed behind the loo via the stud wall the loo is fixed to (RHS of pics).

    Reason for re-work is I realised (when had flooring re-done to vinyl) the centring of the loo over the waste was too far off centre to be properly gas / liquid tight. I know you can get flexis but I prefer MacApline solid waste bend couplers.

    As I had to cut into area behind the loo (from the Hall outside) decided to make an understairs cupboard there and move all plumbing into the loo area.

    So have cut hole in side wall to bring pipes out with elbows. Was lucky to be able to get the dab off both pipes without damage.

    For blobs above the pipes, simply put a nick in the side with architrave cutter (masonry blade) then chiselled off ok, the material is very hard, and didn't dare give the block wall sufficient welly to get them off with just a chisel.

    The cold feed was simply originally fixed to the blocks with copper clips by the original house builder, and then plastic backed wool stuck over.

    Questions: Is the function of that wool to protect the copper from the dab material ?

    And for any I remove - what simple material to wrap/cover the pipe in ? (or just leave as is ?)

    Anything adhesive backed would be tricky as the pipe is fairly tight against the wall.

    I won't dab over the pipe but fix wooden battens for the drywall repair patch.

    The overflow pipe is just behind the top of the skirting, I'll use three elbows to bring that out the wall above the copper as that overflow pipe needs to be on the nearest side of the loo, otherwise I'll end up with one of my amateur oil rig refineries of pipe outside the wall.

    Aside: I've heated larger plastic waste pipe to bend in the past, but very hit and miss (Need a hot air gun . . .) so implement as described above.

    Worry: As I've read the wall construction is not the best recommended, the ~21.5mm (dia of the waste) gap between face of blocks and the drywall does not give any room for manoeuvre and decent pipe covering/trunking..

    I can't blame the contractors because I'm sure they were working to the spec/price of the housebuilder Bryant (now defunct), and the orig buyer.

    I have read that some blocks have been made in the past with excess sulphur that can rot copper pipe...

    (Hindsight) So would seem nice to have put some insulation on the blocks first before nailing the pipe, then covering with another layer before the drywall went on (if space for trunking could not be allowed).

    For the soldered elbow simplest would be a Yorkshire, but my intention is to drill/chip out the block and solder a capillary elbow on.

    I've practised that on a scrap block, also squeezed on a 22mm sleeve around the 15mm to protect it while I first cut out the wall.

    Here we go.


    Last edited: Mar 25, 2019
  2. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    Wow Roy that is a long post !!!! I don’t mean to be rude but are there specific questions in there you need a response to as I have to say I’ve got a bit lost with it
  3. Roy_66

    Roy_66 Member

    Sorry for rambling. Just if you had drywall fitted with dot and dab to blocks, how copper 15mm should be protected, assuming copper clipped to the wall as the building designer didn't allow any more space than about 20mm. And if you repair/modify a section, what to do.

  4. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    Felt lagging just pull on
  5. Roy_66

    Roy_66 Member

  6. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    Spot on
  7. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    If your not dot and dabbing don’t need any

    But hair felt on the copper and some dpc on the wall to save the copper won’t harm
    • Like Like x 1
    • Agree Agree x 1
  8. Roy_66

    Roy_66 Member

    Many thanks Shaun. I'm going to put battens on wall, and may use a bit of dab if I can't get it level. DPC sounds a good idea in addition to felt. Think I've got some somewhere.

    Loo is out now and I've chopped out the wall ready for the fun plumbing bit, prob on Weds. I am the worlds slowest amateur plumber :)


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