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Tapered basin waste !!

Discussion in 'Plumbing and Central Heating' started by slider09, 25 Mar 2019.

  1. slider09

    slider09

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    Hi guys

    My new small cloakroom basin has a tapered waste hole (photo below). Every other waste I have fitted has always been flush with the bottom of the basin. Will a normal waste seal on this? Assuming as the hole tapers in eventually it will form a seal against the washer, but will the washer just get squashed and pulled through the hole?

    Also basin sizes, are these the thread size or the diameter of the hole?

    This hole is 40mm.

    Thanks
     

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  3. Madrab

    Madrab

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    The watertight seal isn't created at the top, it's created under the basin by the big rubber seal and the nut so the top seal isn't that important other than keeping the water in the basin. That being said some of the newer wastes are now tapered slightly too and with the washer added creates a top seal. If worried a little silicone under the top edge will sort it.

    If you mean the 32mm then it is taken from the pipe size used - 32mm/1" 1/4. Basin wastes/waste holes are a nominal standard size.
     
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  4. oldbuffer

    oldbuffer

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    Not sure I agree. If there is no watertight seal between the upper flange of the waste and the upper surface of the basin, water can get down through the threads of the shank of the waste, unless the threads are covered in silicone / other sealant, which can make the waste difficult to remove.

    My personal preference is:
    1. Throw away the thin washer (often looks like white foam) designed to go between the flange and upper basin surface.
    2. Roll a "sausage" about 10mm thick of Plumber's Mait, and fit between flange and upper basin surface.
    3. Tighten back nut to squeeze out excess Plumber's Mait and remove excess. (White spirit cleans up the last bits well).
    4. If slotted waste, make sure overflow slots not blocked, and clean out if necessary.
    5. Remove back nut, fit thick rubber washer (usually black) and tighten back nut. Better still, fit Basin Mate in place of rubber washer.
    6. Connect trap etc. Test basin holds water, and drains without leaks.
    7. Put plug in, overfill basin and test overflow.
    8. If overflow leaks from threads, remove back nut, smear Plumber's Mait around threads under rubber washer / Basin Mate.
    9. Tighten up again and re-test.
     
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  5. slider09

    slider09

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    I’ve gone for a freeflow waste as it’s only a small basin with no overflow. Currently as is it, is no use as when the flange is in contact with the upper basin, the domed top of the waste is still below the level on the basin (it’s in the taper).

    So I was going do as above and ‘pack’ out the underside of the flange with plumbers mait to raise the whole thing up so the domed head is above the taper.

    I picked up a basin mate as well.

    Thanks for all the advice.
     
  6. Madrab

    Madrab

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    If it was running down the outside of the waste down the threads, it still has to get past the bottom seal that is sandwiched between the bottom nut and the bottom face of the basin's waste hole. If the bottom nut/seal is watertight it wouldn't leak no matter whether the top was sealed or not ... I would always consider the bottom seal as the primary, as most installs are slotted.
    Sometimes a little silicone may be needed between the waste body and the throat of the basin waste hole as the washers they supply are usually inadequate or get a basin mate as suggested to seal into that gap between the threads and the throat.
    If the top isn't sealed then you may just lose a little water into the trap if the waste is slotted.

    A little silicone up top is sometime used to fill the gap too if the taper is too much or a thicker seal to lift it, much cleaner & easier to trim out silicone later than try to clean off copious amount of squidgy mate IMO.
     
  7. Nige F

    Nige F

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    Plumbers mate - pah ! Red lead putty(y)
     
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