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Discuss Cistern syphon diaphragm replacement in the Bathrooms, Showers and Wetrooms area at UKPlumbersForums.co.uk.

  1. noname

    noname Member

    I am an occasional diy plumber. The other day I thought it was about time to replace the diaphragm in my Idesl Standard close coupled toilet syphon as the handle often needed to be pumped to get a decent flush. I did not find it a particularly easy job. The toilet did not have a service valve so I had to rely on a leaky gate valve in the loft to shut off the water. I ended up having to fit a flexible connector with a service valve and a Diall cistern inlet valve with a brass shank to replace the existing water inlet valve, as I had managed to strip the plastic thread on the old inlet valve. I bought a replacement ring doughnut rubber on which to seat the cistern. This was advertised as being suitable for an Ideal Standard Close coupled toilet. In fact it was anything but suitable so I then bought a standard conical rubber which I had to cut to shape to fit around the large nut that holds the syphon.

    The rubber diaphragm which I removed had perished and I replaced it with a plastic diaphragm. Having done all that I do not find the flush operation 100% better so I am rather disappointed as it often needs two pumps of the handle unless you use brute force at the first attempt.

    I concluded that this old type of syphon is hardly fit for purpose and I wish I had paid for the services of a plumber who might have used a modern syphon.
    As an aside, can any one explain to me how the Diall water inlet valve shuts off the water? Mine seems to work ok but there is no visible washer that might need replacing at some future date. Diall is, as you will know, is B & Qs own brand.
     
  2. rpm

    rpm Trusted Plumber

    For washer use the word diaphragm. Pressure on the diaphragm stops the water.
     
  3. rpm

    rpm Trusted Plumber

    Replace it with the Dudley split flush valve next time, makes the job a whole lot easier.
     
  4. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    If you can any chance of a pic of the insides ?

    Also was the donut washer like a big o ring ?
     
  5. JCplumb

    JCplumb Plumber

    Did you cut your own diaphragm? Maybe the material isn't ideal. I use DPM.
    Could also be that the water level in the cistern is low (or flush valve too tall) so a larger volume of water needs to be raised to the point where the syphon is made.
     
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  6. JCplumb

    JCplumb Plumber

    Never fitted a Diall valve, never will so can't help you on that one. Buy cheap buy twice, fit anything made by fluidmaster next time.
    Those ideal standard cisterns with their mahoosive donuts are a pain in the backside if you don't get the right donut.
     
  7. rpm

    rpm Trusted Plumber

    Haven`t you seen the doc about your photo fetish yet Shaun? ;):)
     
  8. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Maybe but shhhhh always need more
     
  9. rpm

    rpm Trusted Plumber

    No doubt about it then, you are an addict. :)
     
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  10. JCplumb

    JCplumb Plumber

    I was wrong, that Diall valve is a rebranded, more expensive Flomasta. They are servicable, but they are also made so you can just swap the stem with a new one, for the price of them I'd swap the stem if it failed.
    B and Q version
    Flomasta version
     
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  11. Best

    Best Trusted Plumber Top Contributor!!

    The old syphons are usually fine to just repair if they are in good order. You have perhaps a wrong size syphon washer, or a faulty syphon (split in it, but would be rare), or water level too low.
    Must admit new Dudley syphons are good.
     
  12. noname

    noname Member

    The first donut washer I bought, supposedly for Ideal Standard, was like a large o ring. It was nothing like the one I was replacing but I had bought it before removing the cistern. The second one which I bought and adapted was a B & Q 'bog' standard, thick, circular, straight on the inside, with a curved external side. I do not see any leakage when I flush the toilet but it is very early days. I bought the diaphragm and just had to trim the two ends. The Diall inlet valve seems to be working ok though the instructions that go with it are not much help. It does have a good conical washer and a brass stem howeve and it is very quiet when filling and shutting off.
    The water level is as high as it should be. I hope I do not have to remove the cistern again for a very long time. Thank you all for you responses.
     
  13. SimonG

    SimonG Trusted Plumber Top Contributor!!

    And here in lies the when in doubt give a pro a shout.
     
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